WO2019125388A1 - Spin orbit coupling based oscillator using exchange bias - Google Patents

Spin orbit coupling based oscillator using exchange bias Download PDF

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Publication number
WO2019125388A1
WO2019125388A1 PCT/US2017/067106 US2017067106W WO2019125388A1 WO 2019125388 A1 WO2019125388 A1 WO 2019125388A1 US 2017067106 W US2017067106 W US 2017067106W WO 2019125388 A1 WO2019125388 A1 WO 2019125388A1
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WO
WIPO (PCT)
Prior art keywords
magnet
magnetic
plane
adjacent
interconnect
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PCT/US2017/067106
Other languages
French (fr)
Inventor
Tanay GOSAVI
Sasikanth Manipatruni
Dmitri E. Nikonov
Kaan OGUZ
Ian A. Young
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Intel Corporation
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Priority to PCT/US2017/067106 priority Critical patent/WO2019125388A1/en
Publication of WO2019125388A1 publication Critical patent/WO2019125388A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B15/00—Generation of oscillations using galvano-magnetic devices, e.g. Hall-effect devices, or using superconductivity effects
    • H03B15/006—Generation of oscillations using galvano-magnetic devices, e.g. Hall-effect devices, or using superconductivity effects using spin transfer effects or giant magnetoresistance
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/10—Magnetoresistive devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N50/00—Galvanomagnetic devices
    • H10N50/80—Constructional details
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N59/00—Integrated devices, or assemblies of multiple devices, comprising at least one galvanomagnetic or Hall-effect element covered by groups H10N50/00 - H10N52/00

Definitions

  • Embedded memory with state retention can enable energy and computational efficiency.
  • spin transfer torque based magnetic random access memory suffer from the problem of high voltage and high write current during the programming (e.g., writing) of a bit-cell.
  • large write current e.g., greater than 100 mA
  • voltage e.g., greater than 0.7 V
  • Limited write current also leads to high write error rates or slow switching times (e.g., exceeding 20 ns) in MTJ based MRAM.
  • the presence of a large current flowing through a tunnel barrier leads to reliability issues in magnetic tunnel junctions.
  • Fig. 1A illustrates a magnetization response to an applied magnetic field for a ferromagnet.
  • Fig. IB illustrates a magnetization response to an applied magnetic field for a paramagnet.
  • Figs. 2A-B illustrate a three-dimensional (3D) view and corresponding top view, respectively, of a device having an out-of-plane magnetic tunnel junction (MTJ) stack coupled to a spin orbit coupling (SOC) interconnect.
  • MTJ magnetic tunnel junction
  • SOC spin orbit coupling
  • Fig. 3 illustrates a cross-section of the SOC interconnect with electrons having their spins polarized in-plane and deflected up and down resulting from a flow of charge current.
  • Fig. 4A illustrates a plot showing write energy-delay conditions for one transistor and one MTJ with spin Hall effect (SHE) material compared to traditional MTJs.
  • SHE spin Hall effect
  • Fig. 4B illustrates a plot comparing reliable write times for spin Hall MRAM and spin torque MRAM.
  • Figs. 5A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, and a via having an in-plane magnet adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Figs. 6A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, and a via comprising an in-plane magnet and an anti-ferromagnet (AFM) one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • AFM anti-ferromagnet
  • Figs. 7A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where an AFM is embedded in the SOC interconnect, and a via comprising an in-plane magnet which is adjacent to the AFM, according to some embodiments of the disclosure.
  • Figs. 8A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where an AFM electrode replaces the SOC interconnect, and where the oscillator further comprises a via including an in-plane magnet which is adjacent to the AFM, according to some embodiments of the disclosure.
  • Fig. 9 illustrates a cross-section of a cascaded SOC oscillators with charge based coupling between the SOC interconnects, which produces a charge based spin current excitation, in accordance with some embodiments.
  • Fig. 10 illustrates a scheme of an oscillatory Cellular Neural Network (CNN) that uses the SOC based oscillators, according to some embodiments.
  • CNN Cellular Neural Network
  • Figs. 11A-B illustrate a three terminal (3T) high input impedance Spin Torque
  • STO SOC Oscillator
  • SOC oscillator with built-in Mixer according to some embodiments of the disclosure.
  • Fig. 12A illustrates a plot showing a single-sided amplitude spectrum of an input Radio Frequency (RF) signal which is input to the 3T STO with built-in Mixer, according to some embodiments of the disclosure.
  • RF Radio Frequency
  • Fig. 12B illustrates a plot showing magnetization oscillation produced by the
  • Fig. 12C illustrates a plot showing a single-sided amplitude spectrum of the output of the 3T STO with built-in Mixer, according to some embodiments of the disclosure.
  • Fig. 13A-B illustrate a 3T low input impedance STO or SOC oscillator with built-in Mixer, according to some embodiments of the disclosure.
  • Fig. 14 illustrates an RF detection apparatus for Magnetic Resonance Imaging
  • Fig. 15 illustrates an RF detection apparatus for a wireless receiver having the
  • Fig. 16 illustrates an apparatus, with the 3T STO having built-in Mixer, showing parallel sensing using multiple receiver coils at a single frequency, according to some embodiments of the disclosure.
  • Fig. 17 illustrates an apparatus, with the 3T STO having built-in Mixer, showing parallel sensing with frequency multiplexing, according to some embodiments of the disclosure.
  • Fig. 18 illustrates a sensing array formed with the apparatus of Fig. 16, according to some embodiments of the disclosure.
  • Fig. 19 illustrates a sensing array formed with the apparatus of Fig. 16, according to some embodiments of the disclosure.
  • Fig. 20A illustrates an equivalent vector spin circuit for STO RF detector with locally generated oscillator, according to some embodiments of the disclosure.
  • Fig. 20B illustrates a plot showing tunability of the STO, according to some embodiments of the disclosure.
  • Fig. 21A illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Fig. 21B illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a free magnet structure and a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Fig. 21C illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a fixed magnet structure and one of the free magnets of a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Fig. 21D illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Fig. 21E illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a fixed magnet structure and one of the free magnets of a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Fig. 21F illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a free magnet structure and a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet which is adjacent to an AFM embedded in the SOC interconnect, according to some embodiments of the disclosure.
  • Fig. 22 illustrates a flowchart of a method for forming an SOT or SOC based oscillator, in accordance with some embodiments.
  • Figs. 23A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having in-plane magnetizations, and a via having perpendicular magnet adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Figs. 24A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having in-plane magnetizations, and a via comprising perpendicular magnet and an anti-ferromagnet (AFM) one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • AFM anti-ferromagnet
  • Fig. 25 illustrates a smart device or a computer system or a SoC (System-on-
  • Detection and processing of Radio Frequency (RF) signals at a frontend of a receiver, which is part of a signal chain, is used in RF signal processing.
  • Applications such as Global Positioning System (GPS), Magnetic Resonance Imaging (MRI), and highly attenuated signal receivers can benefit from highly parallel signal acquisitions.
  • GPS Global Positioning System
  • MRI Magnetic Resonance Imaging
  • current RF detection and processing schemes use non-linear multipliers using RF electronics for down conversion of the RF signal to an intermediate frequency (IF) signal.
  • IF intermediate frequency
  • the down conversion is generally performed by a mixer circuit that receives a local oscillating signal.
  • This local oscillating signal is generated by a local oscillator (i.e., a clock source) such as a phase locked loop (PLL).
  • PLL phase locked loop
  • This clock source for up or down frequency conversion may be generated off- chip or by an off-the instrument.
  • MRI apparatus has an off-chip clock source used for up or down conversion of RF input signals.
  • one reason for having a dedicated off-chip clock source is that available clock signals used by the MRI apparatus have frequencies not suitable for down conversion.
  • the number of available channels are limited in existing RF receivers (e.g., 10 to 20 channels), which increases the complexity of implementing highly parallel sensing.
  • the STO is a multi-terminal device (e.g., a three terminal (3T) device or a five terminal (5T) device).
  • the STO is a self-sustained oscillator that operates via injection of spin current from a spin orbit torque electrode or a spin orbit coupling electrode.
  • the STO operates via a transverse exchange bias from a bottom electrode (e.g., a spin orbit torque electrode or a spin orbit coupling electrode).
  • the STO operates via spin injection from a magnetic junction (e.g., spin valve or magnetic tunneling junction (MTJ)) to produce magnetic oscillators in the free magnet layer of the magnetic junction.
  • a magnetic junction e.g., spin valve or magnetic tunneling junction (MTJ)
  • the term“free” or“unfixed” here with reference to a magnet refers to a magnet whose magnetization direction can change along its easy axis upon application of an external field or force (e.g., Oersted field, spin torque, etc.).
  • the term“fixed” or “pinned” here with reference to a magnet refers to a magnet whose magnetization direction is pinned or fixed along an axis and which may not change due to application of an external field (e.g., electrical field, Oersted field, spin torque,).
  • perpendicularly magnetized magnet refers to a magnet having a magnetization which is substantially perpendicular to a plane of the magnet or a device.
  • an in-plane magnet refers to a magnet that has magnetization in a direction substantially along the plane of the magnet.
  • a magnet with a magnetization which is in an x or y direction and is in a range of 0 (or 180 degrees) +/- 20 degrees relative to an x-y plane of a device.
  • a device may generally refer to an apparatus according to the context of the usage of that term.
  • a device may refer to a stack of layers or structures, a single structure or layer, a connection of various structures having active and/or passive elements, etc.
  • a device is a three dimensional structure with a plane along the x-y direction and a height along the z direction of an x-y-z Cartesian coordinate system.
  • the plane of the device may also be the plane of an apparatus which comprises the device.
  • spin Hall current e.g., IsH-controi
  • IsH-controi interacts with the free magnet layer (or structure) to produce self-sustained oscillations/excitations.
  • a second tunneling excitation current Isense-controi
  • the path through the magnetic junction provides a sensing path generating an AC current at the oscillation frequency.
  • the path through the spin Hall electrode provides a path to connect spin Hall oscillators for coupling the state of the oscillators.
  • a STO is formed from a single magnetic junction coupled to a spin orbit coupling electrode.
  • the STO or SOC oscillator comprises an antiferromagnetic (AFM) spin orbit coupling electrode with exchange bias experiencing spin excitation from a magnetic junction and/or SOC electrode or layer.
  • the SOC oscillator comprises a heavy metal SOC layer with exchange bias in-plane magnet experiencing spin excitation from magnetic junction and/or SOC layer.
  • the STO is formed from cascaded magnetic junction devices (e.g., SOC electrode of one device is serially coupled to an SOC electrode of another device).
  • SOC oscillators are formed with in-plane magnets and in plane polarizing layers.
  • SOC oscillators are formed with free magnet(s) having perpendicular magnetic anisotropy (PMA) and PMA polarizing layers.
  • PMA perpendicular magnetic anisotropy
  • SOC oscillators are formed with PMA free magnet and in-plane fixed layer of the magnetic junction.
  • the SOC oscillator is formed with in- plane free magnet and PMA fixed magnet.
  • the SOC oscillator is formed from a magnetic junction in the absence of spin injection.
  • the SOC based oscillator uses exchange bias along the hard axis of the magnetic junction magnets.
  • a SOC based oscillator that comprises a magnetic under-layer via for dipole and exchange coupling.
  • the device comprises a perpendicular magnet in contact with an SOC write electrode (e.g., spin Hall effect write electrode) and a magnetic via to produce dipole/exchange bias fields.
  • SOC write electrode e.g., spin Hall effect write electrode
  • in-plane exchange bias from an AFM and/or an in-plane fixed magnet is used to template the magnetic orientation of the free magnets of the magnetic junction. As such, the free magnets of the magnetic junction provide a strong effective in-plane magnet effect.
  • both an in-plane fixed magnet and an AFM are formed in a via which is coupled to or adjacent to a surface of the SOC electrode such that the magnetic junction is formed on the other surface of the SOC electrode.
  • the SOC electrode comprises an AFM.
  • the via comprises a magnet with fixed in-plane magnetization. Since the AFM effect is provided by the SOC electrode in this example, an additional AFM may not be formed in the via.
  • the in-plane fixed magnet under the SOC electrode has a length longer than a length of the magnetic junction.
  • a length refers to a distance along ay-axis as described with reference to various figures.
  • the in plane magnet is made thick enough so that it is stable.
  • stability generally refers to the permanency of the magnetization direction. An unstable magnet in this example would be one that switches its magnetization upon application of an external field.
  • the AFM comprises Ir and Mn (or any other AFM) which can template the magnetic orientation of the in-plane magnet in the via.
  • the free magnet structure of the magnetic junction comprises at least two free magnets that are coupled by a coupling layer.
  • the coupling layer comprises one or more of: Ru, Os, Hs, Fe, or other similar transition metals from the platinum group of the periodic table.
  • the coupling layer(s) are removed so that the free magnets of the free magnet structure or stack are directly connected with one another forming a single magnet (or a composite magnet).
  • one or more of the free magnets of the free magnet structure of the magnetic junction comprises a composite magnet.
  • the composite magnet may be a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy, and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
  • the fixed magnet of the magnetic junction also comprises a composite magnet.
  • Some embodiments describe a STO or SOC oscillator based radio frequency
  • the RF detector includes an STO with an integrated mixer (e.g., built-in mixer) and formed using a magnetic junction and a spin orbit coupling layer (e.g., a layer that exhibits spin Hall effect).
  • the RF detector is a multiplier that naturally provides a local clock demodulation frequency via inherent precessional dynamics of nanomagnets.
  • the 3T STO configuration is used to down convert the input RF signal to a corresponding base band as set by the local STO.
  • signals are represented with lines. Some lines may be thicker, to indicate more constituent signal paths, and/or have arrows at one or more ends, to indicate primary information flow direction. Such indications are not intended to be limiting. Rather, the lines are used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit or a logical unit. Any represented signal, as dictated by design needs or preferences, may actually comprise one or more signals that may travel in either direction and may be implemented with any suitable type of signal scheme. [0056] Throughout the specification, and in the claims, the term "connected” means a direct connection, such as electrical, mechanical, or magnetic connection between the things that are connected, without any intermediary devices.
  • Coupled means a direct or indirect connection, such as a direct electrical, mechanical, or magnetic connection between the things that are connected or an indirect connection, through one or more passive or active intermediary devices.
  • circuit or“module” may refer to one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function.
  • signal may refer to at least one current signal, voltage signal, magnetic signal, or data/clock signal.
  • the meaning of “a,” “an,” and “the” include plural references.
  • the meaning of “in” includes “in” and “on.”
  • the term“scaling” generally refers to converting a design (schematic and layout) from one process technology to another process technology and subsequently being reduced in layout area.
  • the term“scaling” generally also refers to downsizing layout and devices within the same technology node.
  • the term“scaling” may also refer to adjusting (e.g., slowing down or speeding up - i.e. scaling down, or scaling up respectively) of a signal frequency relative to another parameter, for example, power supply level.
  • the terms “substantially,”“close,”“approximately,”“near,” and“about,” generally refer to being within +/- 10% of a target value.
  • phrases“A and/or B” and“A or B” mean (A), (B), or (A and B).
  • phrase“A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).
  • spin spin and“magnetic moment” are used equivalently. More rigorously, the direction of the spin is opposite to that of the magnetic moment, and the charge of the particle is negative (such as in the case of electron).
  • Fig. 1A illustrates a magnetization hysteresis plot 100 for ferromagnet (FM)
  • the plot shows magnetization response to an applied magnetic field for ferromagnet 101.
  • the x-axis of plot 100 is magnetic field ⁇ ’ while the y-axis is magnetization‘m’.
  • the relationship between ⁇ ’ and‘m’ is not linear and results in a hysteresis loop as shown by curves 102 and 103.
  • the maximum and minimum magnetic field regions of the hysteresis loop correspond to saturated magnetization configurations 104 and 106, respectively.
  • saturated magnetization configurations 104 and 106 FM 101 has stable magnetizations.
  • FM 101 does not have a definite value of magnetization, but rather depends on the history of applied magnetic fields.
  • the magnetization of FM 101 in configuration 105 can be either in the +x direction or the -x direction for an in-plane FM.
  • changing or switching the state of FM 101 from one magnetization direction (e.g., configuration 104) to another magnetization direction (e.g., configuration 106) is time consuming resulting in slower nanomagnets response time. It is associated with the intrinsic energy of switching proportional to the area in the graph contained between curves 102 and 103.
  • Fig. IB illustrates magnetization plot 120 for paramagnet 121.
  • Plot 120 shows the magnetization response to an applied magnetic field for paramagnet 121.
  • the x-axis of plot 120 is magnetic field ⁇ ’ while the y-axis is magnetization‘m’.
  • a paramagnet as opposed to a ferromagnet, exhibits magnetization when a magnetic field is applied to it.
  • Paramagnets generally have magnetic permeability greater or equal to one and hence are attracted to magnetic fields.
  • the magnetic plot 120 of Fig. IB does not exhibit hysteresis which allows for faster switching speeds and smaller switching energies between the two saturated magnetization configurations 124 and 126 of curve 122.
  • paramagnet 121 comprises a material which includes one or more of: Platinum(Pt), Palladium (Pd), Tungsten (W), Cerium (Ce), Aluminum (Al), Lithium (Li), Magnesium (Mg), Sodium (Na), CnCh (chromium oxide), CoO (cobalt oxide), Dysprosium (Dy), Dy 2 0 (dysprosium oxide), Erbium (Er), Er 2 0 3 (Erbium oxide), Europium (Eu), EmCb (Europium oxide), Gadolinium (Gd), Gadolinium oxide (Gd 2 0 3 ), FeO and Fe 2 0 3 (Iron oxide), Neodymium (Nd), Nd 2 0 3 (Neodymium oxide), K0 2 (potassium superoxide), praseodymium (Pr), Samarium (Sm), Sm 2 0 3 (samarium oxide), Terbium (Tb), Tb
  • the magnet can be either a FM or a paramagnet.
  • Figs. 2A-B illustrate a three-dimensional (3D) view 200 and corresponding top view 220, respectively, of a device (also referred to as device 200) having an out-of-plane magnetic tunnel junction (MTJ) stack coupled to a spin orbit coupling (SOC) interconnect, where the MTJ stack includes a free magnet layer much smaller than a length of the SOC interconnect.
  • MTJ magnetic tunnel junction
  • SOC spin orbit coupling
  • the stack of layers having magnetic juncti on 221 is coupled to an electrode 222 comprising spin Hall effect (SHE) or SOC material, where the SHE material converts charge current Iw (or write current) to spin polarized current Is.
  • the device of Fig. 2A forms a three-terminal memory cell with SHE induced write mechanism and MTJ based read-out.
  • the device of Fig. 2A comprises magnetic junction 221, SHE Interconnect or electrode 222, and non-magnetic metal(s) 223a/b.
  • MTJ 221 comprises layers 22la, 22lb, and 22lc.
  • layers 22la and 22lc are ferromagnetic layers.
  • layer 22lb is a metal or a tunneling dielectric.
  • layer 22lb is metal or a metal oxide (e.g., a non-magnetic metal such as Al and/or its oxide) and when the magnetic junction is a tunneling junction, then layer 22lb is a dielectric (e.g. MgO, AhCh).
  • a metal oxide e.g., a non-magnetic metal such as Al and/or its oxide
  • layer 22lb is a dielectric (e.g. MgO, AhCh).
  • MgO, AhCh a dielectric
  • One or both ends along the horizontal direction of SHE Interconnect 222 is formed of non magnetic metals 223a/b. Additional layers 22ld, 22le, 22lf, and 22lg can also be stacked on top of layer 22lc.
  • layer 22lg is a non-magnetic metal electrode.
  • the magnetic junction is described as a magnetic tunneling junction (MTJ).
  • the embodiments are also applicable for spin valves.
  • a wide combination of materials can be used for material stacking of magnetic j unction 221.
  • the stack of layers 22la, 22lb, 22lc, 22ld, 22le, 22lf, and 22lg are formed of materials which include: Co x Fe y B z , MgO, Co x Fe y B z , Ru, Co x Fe y B z , IrMn, and Ru, respectively, where‘x,’‘y,’ and‘z’ are fractions of elements in the alloys.
  • Other materials may also be used to form MTJ 221.
  • MTJ 221 stack comprises free magnetic layer 22la, MgO tunneling oxide 22lb, a fixed magnetic layer 22lc/d/e which is a combination of CoFe, Ru, and CoFe layers, respectively, referred to as Synthetic Anti- Ferromagnet (SAF), and an Anti-Ferromagnet (AFM) layer 22lf.
  • SAF Synthetic Anti- Ferromagnet
  • AFM Anti-Ferromagnet
  • the SAF layer has the property that the magnetizations in the two CoFe layers are opposite, and allows for cancelling the dipole fields around the free magnetic layer such that a stray dipole field will not control the free magnetic layer.
  • the free and fixed magnetic layers are formed of CFGG (i.e., Cobalt (Co), Iron (Fe), Germanium (Ge), or Gallium (Ga) or a combination of them).
  • FM 22la/c are formed from Heusler alloys.
  • Heusler alloys are ferromagnetic metal alloys based on a Heusler phase. Heusler phases are intermetallic with certain composition and face-centered cubic crystal structure. The ferromagnetic property of the Heusler alloys are a result of a double-exchange mechanism between neighboring magnetic ions.
  • the Heusler alloy includes one of: Cu 2 MnAl, Cu 2 MnIn, Cu 2 MnSn, NfiMnAl, NfiMnln, NfiMnSn, NfiMnSb, Ni 2 MnGa Co 2 MnAl, Co 2 MnSi, Co 2 MnGa, Co 2 MnGe, Pd 2 MnAl, Pd 2 MnIn, Pd 2 MnSn, Pd 2 MnSb, Co 2 FeSi, Co 2 FeAl, Fe 2 VAl, Mn 2 VGa, Co 2 FeGe, MnGa, or MnGaRu.
  • fixed magnet layer 22 lc is a magnet with perpendicular magnetic anisotropy (PMA).
  • PMA perpendicular magnetic anisotropy
  • fixed magnet structure 22 lc has a magnetization pointing along the z-direction and is perpendicular to the x-y plane of the device 200.
  • the magnet with PMA comprises a stack of materials, wherein the materials for the stack are selected from a group consisting of: Co and Pt; Co and Pd; Co and Ni; MgO, CoFeB, Ta, CoFeB, and MgO; MgO, CoFeB, W, CoFeB, and MgO; MgO, CoFeB, V, CoFeB, and MgO; MgO, CoFeB, Mo, CoFeB, and MgO; Mn x Ga y ; Materials with Llo symmetry; and materials with tetragonal crystal structure.
  • the magnet with PMA is formed of a single layer of one or more materials. In some embodiments, the single layer is formed of MnGa.
  • Llo is a crystallographic derivative structure of an FCC (face centered cubic lattice) structure and has two of the faces occupied by one type of atom and the comer and the other face occupied with the second type of atom.
  • FCC face centered cubic lattice
  • the magnetization vector usually is along the [0 0 1] axis of the crystal.
  • SHE Interconnect 222 includes 3D materials such as one or more of b-Tantalum (b-Ta), BiSb, Ta, b-Tungsten (b-W), W, Pt, Copper (Cu) doped with elements such as Iridium, Bismuth and any of the elements of 3d, 4d, 5d and 4f, 5f periodic groups in the Periodic Table which may exhibit high spin orbit coupling.
  • SHE interconnect 122 comprises a spin orbit 2D material which includes one or more of: graphene, BiSe 2 , B1S2, BiSe x Te2-x, BiSb.TiS. WS2, M0S2, TiSe2, ⁇ VSe2.
  • the SHE interconnect 222 comprises spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material.
  • the SHE interconnect 222 comprises a spin orbit material which includes materials that exhibit Rashba-Bychkov effect.
  • material which includes materials that exhibit Rashba-Bychkov effect comprises materials ROCh2, where‘R’ includes one or more of: La, Ce, Pr, Nd, Sr, Sc, Ga, Al, or In, and where“Ch” is a chalcogenide which includes one or more of: S, Se, or Te.
  • SHE Interconnect 222 transitions into high
  • the non-magnetic metal(s) 223a/b include one or more of: Cu, Co, a-Ta, Al, CuSi, or NiSi.
  • the magnetization direction of fixed magnetic layer 22 lc is perpendicular relative to the magnetization direction of free magnetic layer 22la (e.g., magnetization directions of the free and fixed magnetic layers are not parallel, rather they are orthogonal).
  • the magnetization direction of free magnetic layer 221 a is along the x-y plane of device 200 while the magnetization direction of fixed magnetic layer 22 lc is perpendicular to the x-y plane of device 200.
  • magnetization direction of fixed magnetic layer 22 la is along the x-y plane of device 200 while the magnetization direction of free magnetic layer 221 c is perpendicular to the x-y plane of device 200.
  • the thickness of a ferromagnetic layer may determine its equilibrium magnetization direction. For example, when the thickness of the ferromagnetic layer 22la/c is above a certain threshold (depending on the material of the magnet, e.g. approximately 1.5 nm for CoFe), then the ferromagnetic layer exhibits magnetization direction which is in-plane. Likewise, when the thickness of the ferromagnetic layer 22la/c is below a certain threshold (depending on the material of the magnet), then the ferromagnetic layer 22la/c exhibits magnetization direction which is perpendicular to the plane of the magnetic layer. [0081] Other factors may also determine the direction of magnetization.
  • factors such as surface anisotropy (depending on the adjacent layers or a multi-layer composition of the ferromagnetic layer) and/or crystalline anisotropy (depending on stress and the crystal lattice structure modification such as FCC (face centered cubic lattice), BCC (body centered cubic lattice), or Llo-type of crystals, where Llo is a type of crystal class which exhibits perpendicular magnetizations), can also determine the direction of magnetization.
  • FCC face centered cubic lattice
  • BCC body centered cubic lattice
  • Llo-type of crystals where Llo is a type of crystal class which exhibits perpendicular magnetizations
  • the applied current I w is converted into spin current by SHE
  • Interconnect 222 also referred to as the spin orbit coupling interconnect. This spin current switches the direction of magnetization of the free layer and thus changes the resistance of MTJ 221. However, to read out the state of MTJ 221, a sensing mechanism is needed to sense the resistance change.
  • the magnetic cell is written by applying a charge current via SHE
  • the direction of the magnetic writing in free magnet layer 221 a is decided by the direction of the applied charge current.
  • Positive currents e.g., currents flowing in the +y direction
  • a spin injection current with transport direction (along the +z direction) and spins pointing to the +x direction.
  • the injected spin current in turn produces spin torque to align the free magnet 22 la (coupled to the SHE layer 222 of SHE material) in the +x direction.
  • Negative currents e.g., currents flowing in the -y direction
  • the injected spin current in turn produces spin torque to align the free magnet 22 la (coupled to the SHE material of layer 222) in the -x direction.
  • the directions of spin polarization and thus of the free layer magnetization alignment are reversed compared to the above.
  • Fig. 3 illustrates a cross-section 300 of the SOC interconnect with electrons having their spins polarized in-plane and deflected up and down resulting from a flow of charge current.
  • positive charge current represented by J c produces spin-front (e.g., in the +x direction) polarized current 301 and spin-back (e.g., in the -x direction) polarized current 302.
  • the injected spin current l s generated by a charge current I c in the write electrode 222 is given by:
  • the vector of spin current I s I f — / j, points in the direction of transferred magnetic moment and has the magnitude of the difference of currents with spin along and opposite to the spin polarization direction
  • z is the unit vector perpendicular to the interface
  • P SHE is the spin Hall injection efficiency which is the ratio of magnitude of transverse spin current to lateral charge current
  • w is the width of the magnet
  • t is the thickness of the SHE
  • S f is the spin flip length in SHE Interconnect 222
  • Q 5HE is the spin Hall angle for SHE Interconnect 222 to free ferromagnetic layer interface.
  • the generated spin up and down currents 301/302 (e.g ., / s ) are described as a vector cross-product given by:
  • This spin to charge conversion is based on Tunnel Magneto Resistance (TMR) which is highly limited in the signal strength generated.
  • TMR Tunnel Magneto Resistance
  • the TMR based spin to charge conversion has low efficiency (e.g., less than one).
  • perpendicularly magnetized free magnet layer coupled to SOC interconnect 222 can be switched inefficiently and in the presence of a significant external magnetic field. This means forming devices (e.g., logic and memory) with perpendicular magnetic anisotropy (PMA) are generally a challenge with SOC interconnect 222.
  • perpendicularly magnetized free magnet refers to a magnet having magnetization which is perpendicular to the plane of the magnet as opposed to in-plane magnet that has magnetization in a direction along the plane of the magnet.
  • Fig. 4A illustrates a plot 420 showing write energy-delay conditions for one transistor and one MTJ with spin Hall effect (SHE) material compared to traditional MTJs.
  • SHE spin Hall effect
  • Fig. 4B illustrates plot 430 showing write energy-delay conditions for one transistor and one magnetic tunnel junction (MTJ) with spin Hall effect (SHE) material compared to traditional MTJs.
  • x-axis is energy per write operation in femto-Joules (fJ) while the y-axis is delay in nano-seconds (ns).
  • the energy-delay trajectory of SHE and MTJ devices are compared for in-plane magnet switching as the applied write voltage is varied.
  • the energy-delay relationship (for in-plane switching) can be written as: where R write is the write resistance of the device (resistance of SHE electrode or resistance of MTJ-P or MTJ-AP, where MTJ-P is a MTJ with parallel magnetizations while MTJ-AP is an MTJ with anti-parallel magnetizations, m 0 is vacuum permeability, e is the electron charge.
  • R write is the write resistance of the device (resistance of SHE electrode or resistance of MTJ-P or MTJ-AP, where MTJ-P is a MTJ with parallel magnetizations while MTJ-AP is an MTJ with anti-parallel magnetizations, m 0 is vacuum permeability, e is the electron charge.
  • the equation shows that the energy at a given delay is directly proportional to the square of the
  • t 0 / j v aries as the spin polarization varies for various SHE metal electrodes (e.g., 423, 424, 425).
  • Plot 420 shows five curves 421, 422, 423, 424, and 425.
  • Curves 421 and 422 show write energy-delay conditions using traditional MTJ devices without SHE material.
  • curve 421 shows the write energy-delay condition caused by switching a magnet from anti-parallel (AP) to parallel (P) state
  • curve 422 shows the write energy-delay condition caused by switching a magnet from P to AP state
  • Curves 422, 423, and 424 show write energy-delay conditions of an MTJ with SHE material.
  • write energy-delay conditions of an MTJ with SHE material is much lower than the write energy-delay conditions of an MTJ without SHE material. While the write energy-delay of an MTJ with SHE material improves over a traditional MTJ without SHE material, further improvement in write energy-delay is desired.
  • Fig. 4B illustrates plot 430 comparing reliable write times for spin Hall
  • Waveform 431 is the write time for in-plane MTJ
  • waveform 432 is the write time for PMA MTJ
  • waveform 433 is the write time for spin Hall MTJ.
  • the cases considered here assume a 30 X 60 nm magnet with 40 kT energy barrier and 3.5 nm SHE electrode thicknesses.
  • the energy- delay trajectories of the devices are obtained assuming a voltage sweep from 0 V to 0.7 V in accordance to voltage restrictions of scaled CMOS.
  • the energy-delay trajectory of the SHE- MTJ devices exhibits broadly two operating regions A) Region 1 where the energy-delay
  • the energy-delay trajectory of the STT-MTJ (spin transfer torque MTJ) devices is limited with a minimum delay of 1 ns for in-plane devices at 0.7 V maximum applied voltage, the switching energy for P-AP and AP-P are in the range of 1 pJ/write.
  • the energy-delay trajectory of SHE-MTJ (in-plane anisotropy) devices can enable switching times as low as 20 ps (b-W with 0.7 V, 20 fj/bit) or switching energy as small as 2 fj (b-W with 0.1 V, 1.5 ns switching time).
  • Figs. 5A-B illustrate a 3D view 500 and corresponding cross-section view
  • the oscillator of Fig. 5A is similar to the device of Fig. 2A except that the free magnet 22 la of Fig. 2A is replaced with a structure comprising a stack of layers or films.
  • the magnetic junction is illustrated by reference sign 521 where the layers under layer 22lb (e.g., dielectric or metal/metal-oxide) together form the structure comprising the free magnet of the junction.
  • the structure replacing free magnet 22 la comprises at least two free magnets 52laa and 52lac with a coupling layer 52lab between them, where one of the free magnet couples to (or is adjacent to) the SOC electrode 222 while the other free magnet of the structure couples to or is adjacent to a dielectric (e.g., when the magnetic junction is an MTJ) or a metal or its oxide (e.g., when the magnetic junction is a spin valve).
  • a dielectric e.g., when the magnetic junction is an MTJ
  • a metal or its oxide e.g., when the magnetic junction is a spin valve
  • the structure comprises a first free magnet 52laa having perpendicular magnetization that can point substantially along the + z-axis or - z-axis according to an external field (e.g., spin torque, spin coupling, electric field); a coupling layer 52lab; and a second free magnet 52 lac having perpendicular magnetization that can point substantially along the + z-axis or - z-axis.
  • the second free magnet 52lac is adjacent to layer 22lb (e.g., dielectric or metal/metal-oxide).
  • the oscillator of Fig. 5A includes an in-plane fixed magnet 524 adjacent to one of the surfaces of the SOC interconnect 222 such that the magnetic junction 521 is formed on the other surface opposite to the surface of the SOC interconnect 222.
  • the in-plane fixed magnet 524 is thick or long enough in dimensions that results in a stable in-plane magnet that applies an effective in plane field on the perpendicular free magnets 52laa and/or 52 lac for faster switching of free magnets 52laa and/or 52lac.
  • the effective in-plane field can be applied via exchange bias interaction or dipole coupling from the in-plane free magnet 524. As such, an oscillating signal is generated.
  • the coupling layer 521 ab includes one or more of: Ru,
  • magnets 52laa, 52 lac, and 524 comprise CFGG.
  • magnets 52laa, 52lac, and 524 are formed from Heusler alloys.
  • the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
  • the Heusler alloy includes one of: Cu 2 MnAl, Cu 2 MnIn, Cu 2 MnSn, Ni 2 MnAl, Ni 2 MnIn, Ni 2 MnSn, Ni 2 MnSb, Ni 2 MnGa Co 2 MnAl, Co 2 MnSi,
  • magnets 52laa and 52 lac with PMA comprises a stack of materials, wherein the materials for the stack are selected from a group comprising: Co and Pt; Co and Pd; Co and Ni; MgO, CoFeB, Ta, CoFeB, and MgO; MgO, CoFeB, W, CoFeB, and MgO; MgO, CoFeB, V, CoFeB, and MgO; MgO, CoFeB, Mo, CoFeB, and MgO;
  • the magnet with PMA is formed of a single layer of one or more materials.
  • the single layer comprises Mn and Ga (e.g., MnGa).
  • the embodiments of Figs. 5A-B are illustrated with reference to magnets having PMA magnetizations, the embodiments are also applicable to magnets having in-plane magnetizations (not shown).
  • the free magnets 52laa and 52lac, and fixed magnet 22lc are in-plane magnets with in-plane magnetizations
  • the fixed magnet 524 has perpendicular fixed magnetization to provide an effective out-of-plane field to the in-plane free magnets 521 aa and/or 521 ac.
  • the in-plane fixed magnet 524 is formed in a via, also referred to as a magnetic via. For example, a hole is first formed and then filled with materials for making an in-plane fixed magnet.
  • the STO operates via a transverse exchange bias from a bottom electrode 222 (e.g., a spin orbit torque electrode or a spin orbit coupling electrode).
  • a bottom electrode 222 e.g., a spin orbit torque electrode or a spin orbit coupling electrode.
  • the STO operates via spin injection from a magnetic junction 521 (e.g., spin valve or magnetic tunneling junction (MTJ)) to produce magnetic oscillators in the free magnet layer 52laa/ac of the magnetic junction 531.
  • a magnetic junction 521 e.g., spin valve or magnetic tunneling junction (MTJ)
  • spin Hall current e.g., IsH-controi
  • IsH-controi interacts with the free magnet layer (or structure) 52laa/ac to produce self-sustained oscillations/excitations.
  • a second tunneling excitation current Isense-controi
  • the path through the magnetic junction 531 provides a sensing path generating an AC current at the oscillation frequency.
  • the path through the spin Hall electrode 222 provides a path to connect spin Hall oscillators for coupling the state of the oscillators.
  • Figs. 6A-B illustrate a 3D view 600 and corresponding cross-section view 620, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, and a via comprising an in-plane magnet and an anti- ferromagnet (AFM) one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • the oscillator of Fig. 6A is similar to the oscillator of Fig. 5A, but for addition of AFM 625 in the magnetic via.
  • the in-plane fixed magnet 524 of the magnetic via is coupled to or is adjacent to an in-plane anti- ferromagnet (AFM) or synthetic AFM (SAF) 625 also formed in the magnetic via.
  • AFM in-plane anti- ferromagnet
  • SAF synthetic AFM
  • the order of the AFM 625 and in-plane fixed magnet 524 can be switched.
  • AFM 625 is adjacent to SOC interconnect 222 while the in-plane fixed magnet 524 is below AFM 625 and not in direct contact with SOC interconnect 625.
  • AFM or SAF 625 comprises a material which includes one of: Ir, Pt, Mn, Pd, or Fe.
  • AFM or SAF 625 is a quasi-two- dimensional triangular AFM including Ni(i -X) M x Ga2S4, where‘M’ includes one of: Mn, Fe,
  • AFM or SAF 625 comprises a pair of fixed magnets 625a and 625c with in-plane magnetizations, and a coupling layer 625b between the fixed magnets 625a and 625c.
  • the materials for the fixed magnets 625a/c can be according to any of the materials for magnets discussed herein.
  • the material for coupling layer 625b can be the same material (or selected from the same group of materials) as that of coupling layer 52lab.
  • the oscillator of Fig. 6A performs similarly to the oscillator of Fig. 5A, and provides an oscillating signal.
  • Figs. 7A-B illustrate a 3D view 700 and corresponding cross-section view 720, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where an AFM is embedded in the SOC interconnect, and a via comprising an in-plane magnet which is adjacent to the AFM, according to some embodiments of the disclosure.
  • the oscillator of Fig. 7A is similar to the oscillator of Fig.
  • AFM 722 can behave as an etch stop layer when fabricating SOC interconnect 222. As such, one or more additional processes for forming an etch stop layer is/are removed. In various embodiments, AFM 722 assists with keeping the magnetization of magnet 525 stable with in-plane magnetization. In some embodiments, AFM 722 also comprises a pair of fixed magnets (not shown) with in plane magnetizations, and a coupling layer between the fixed magnets like AFM 625.
  • the oscillator of Fig. 7A performs similarly to the oscillators of Figs. 5-6, and provides an oscillating signal.
  • Figs. 8A-B illustrate a 3D view 800 and corresponding cross-section view 820, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where an AFM electrode replaces the SOC interconnect, and where the oscillator further comprises a via including an in-plane magnet which is adjacent to the AFM, according to some embodiments of the disclosure.
  • the device of Fig. 8A is similar to the device of Fig. 5A except that the SOC interconnect 222 is replaced with AFM interconnect 722.
  • the oscillator of Fig. 8A performs similarly to the oscillators of Figs. 5-7, and provides an oscillating signal.
  • Fig. 9 illustrates a cross-section 900 of a cascaded SOC oscillators with charge based coupling between the SOC interconnects, which produces a charge based spin current excitation, in accordance with some embodiments.
  • SOC oscillators 901 and 902 are cascaded such that the SOC interconnects of SOC oscillator 901 and SOC oscillator 902 are coupled together.
  • the SOC oscillators are based on the oscillator of Fig. 5B.
  • Oscillators can be connected together in multiple ways.
  • the spin orbit electrode 222 of one MTJ can be connected to another MTJ.
  • the output of one oscillator read across the MTJ can also be fed to the other MTJ by connecting layer 22lg via a common electrode.
  • the oscillators work in parallel configuration.
  • Other form of coupling replay on spacing the oscillators close to one another allowing for their magnetic fields to be coupled by proximity effect, in accordance with some embodiments.
  • Fig. 10 illustrates a scheme 1000 of an oscillatory Cellular Neural Network (CNN) that uses the SOC based oscillators, according to some embodiments.
  • CNN are a parallel computing networks in which communication is allowed between neighboring units.
  • CNN processors are a system of nonlinear processing units. These nonlinear processing units may be a finite, fixed-number, fixed-location, fixed-topology, locally interconnected, multiple-input, and/or single-output.
  • CNN processors can be used for image processing and pattern recognition.
  • One such scheme used for image processing is a rectangular array of SOT or SOC oscillators as shown in Fig. 10.
  • the SOT or SOC oscillators (OSCs) are coupled together via inductors L0.
  • an NxN array of OSCs lOOloo through IOOINN are shown, where each SOT or SOC OSC is a cell or neuron, and where‘N’ is an integer.
  • Figs. 11A-B illustrate a three terminal (3T) high input impedance STO or SOC oscillator 1100 with built-in Mixer, according to some embodiments of the disclosure.
  • apparatus 1100 comprises STO 1101 (e.g., any one of SOT or SOC oscillators of Figs. 5-8 and Fig. 22), Bias-T (or Bias-Tee) network 1102, Isolator 1103, and first, second, and third non-magnetic conductors H04a, H04b, and H04c, respectively.
  • STO 1101 e.g., any one of SOT or SOC oscillators of Figs. 5-8 and Fig. 22
  • Bias-T or Bias-Tee
  • Isolator 1103 Isolator 1103
  • first, second, and third non-magnetic conductors H04a, H04b, and H04c respectively.
  • STO 1101 includes a magnetic junction having free and fixed magnetic layers such that one of the magnetic layers is an in-plane magnet and another is a perpendicular magnet.
  • the free and fixed magnetic layers are separated by a metal.
  • the magnetic junction is a spin valve.
  • the free and fixed magnetic layers are separated by a dielectric (e.g., MgO, AI2O3).
  • the magnetic junction is a magnetic tunneling junction (MTJ).
  • STO 1101 includes a spin orbit coupling (SOC) layer (e.g., interconnect 222) coupled to the free magnet 52laa of the magnetic junction (e.g., 521)
  • SOC layer is biased by a SOC DC bias. In some embodiments, this DC bias defines in-part the center frequency of oscillation of STO 1101.
  • the SOC layer is coupled to first and second non-magnetic conductors 1 l04a/b on either ends of the SOC layer, respectively.
  • the fixed magnet of STO 1101 is coupled directly or indirectly to a metal electrode which in turn is coupled to the third non-magnetic conductor 1 l04c.
  • an input RF signal (RFIN) is provided to the first non-magnetic conductor 1 l04a.
  • RFIN input RF signal
  • the input impedance ZIN of apparatus 1100 is high because the impedance looking into apparatus 1100 sees non-magnetic conductors l04a/b.
  • Bias-T 1102 biases STO 1101 with a DC bias.
  • this DC bias defines in-part the center frequency of oscillation of STO 1101.
  • Bias-T 1102 is a three port network (often arranged in a T shape) which is used for setting the DC bias point of STO 1101 without disturbing other components.
  • Bias-T 1102 is a diplexer.
  • Bias-T 1102 can be viewed as an ideal capacitor that allows AC (alternating current) through but blocks the DC bias and an ideal inductor that blocks AC but allows DC (direct current).
  • the low frequency port of Bias-T 1102 is used to set the bias.
  • the low frequency port receives the DC bias and control.
  • a first high frequency port of Bias-T 1102 passes the RF signals but blocks the biasing levels. For example, low frequency IF signal, which is down modulated from the RF input at the Zin port by the STO, is received at the output of Isolator 1103 (e.g., IF OUT).
  • Isolator 1103 e.g., IF OUT
  • the first high frequency port of Bias-T 1102 is coupled to Isolator 1103.
  • a second high frequency port of Bias-T 1102 passes both the RF signal and the DC bias.
  • the second high frequency port of Bias-T 1102 is coupled to third non-magnetic conductor 1104a.
  • Isolator 1103 isolates Bias-T 1102 from other components.
  • Isolator 1103 is a non-reciprocal device, with a non- symmetric scattering matrix.
  • Isolator 1103 suppresses backward reflection of RF signal from the detection circuitry (i.e., from STO 1101).
  • an intermediate frequency output is provided across Isolator 1103 and second non-magnetic conductor 1 l04b.
  • This IFOUT is the down converted RFIN signal.
  • the output impedance ZOUT across Isolator 1103 and second non-magnetic conductor 1 l04b is high impedance.
  • another Isolator (not shown) is provided at the input and coupled to non-magnetic conductor 1104a. As such, RFIN is provided uni-directi onally to the non-magnetic conductor 1104a.
  • Isolator 1103 is optional and can be removed.
  • STO 1101 receives RFIN and down converts it to IFOUT using the oscillation behavior of STO 1101 and its built-in mixer function.
  • the oscillation behavior of STO 1101 is achieved from the metastability of the perpendicular magnet and the in-plane magnet.
  • STO 1101 begins to oscillate and mixes the RF signal to a lower frequency (e.g., down converts it).
  • a filter is used with a roll-off. In some embodiments, this filter is placed after Isolator 1103 as illustrated by filters 1602 in Fig. 16.
  • Fig. 11B is similar to Fig. 11A but for showing the oscillator 1101 which can be any of the devices of Figs. 5-9 and Fig. 22
  • Fig. 12A illustrates a plot 1200 showing a single-sided amplitude spectrum of an input RF signal which is input to the 3T STO with built-in Mixer, according to some embodiments of the disclosure.
  • x-axis is frequency (GHz)
  • y-axis is magnitude of the power spectral density of the measured current from MTJ.
  • Fig. 12B illustrates a plot 1220 showing magnetization oscillation produced by the 3T STO with built-in Mixer, according to some embodiments of the disclosure.
  • the oscillation is produced by the metastability caused by the
  • plot 1220 shows the magnetic dynamics of STO 1101 with continuous oscillations centered at 7.5 GHz.
  • Fig. 12C illustrates a plot 1230 showing a single-sided amplitude spectrum of the output of the 3T STO with built-in Mixer, according to some embodiments of the disclosure.
  • Plot 1230 shows that IFouThas a frequency of 1.5 GHz which is produced by down converting of RFIN from 9 GHz via STO 1101, in accordance with some embodiments.
  • the frequency of the down converted signal can be adjusted by adjusting the DC bias and control to Bias-T 1102 (which in turn biases STO 1101) and/or the DC bias of SOC bias.
  • the down converted signal is detected and processed by a digital signal processing logic (not shown).
  • Fig. 13A-B illustrate a 3T low input impedance STO or SOC oscillator 1300 with built-in Mixer, according to some embodiments of the disclosure.
  • STO 1101 is oriented such that ZIN is low compared to ZIN of apparatus 1100.
  • RFIN sees the SOC layer of STO 1101 instead of first and third non-magnetic conductors 1 l04a/c (as in apparatus 1100)
  • RFIN sees lower impedance because the SOC layer 222 has lower impedance than first and third non-magnetic conductors H04a/c.
  • apparatus 1300 can be used for RF applications that desire lower input impedance while apparatus 1100 can be used for RF applications that desire higher input impedance.
  • Fig. 13B is similar to Fig. 13A but for showing the oscillator 1101 which can be any of the devices of Figs. 5-9 and Fig. 22
  • Fig. 14 illustrates an RF detection apparatus 1400 for Magnetic Resonance Imaging (MRI) having the 3T STO with built-in Mixer, according to some embodiments of the disclosure, according to some embodiments of the disclosure.
  • MRI Magnetic Resonance Imaging
  • apparatus 1400 comprises an RF Receiver (Rx) 1401, Balun 1402, Low Noise Amplifier 1403, STO apparatus 1404 (e.g., apparatus 1100, 1120, 1300, 1320), and Digital Signal Processing logic 1405.
  • Rx RF Receiver
  • STO apparatus 1404 e.g., apparatus 1100, 1120, 1300, 1320
  • RF Rx 1401 is an Rx coil or antenna array with a preferred quality factor Q (e.g., in the range of 1 to 100) tuned to the incoming
  • RF Rx 1401 is illustrated as an RF receiver coil with controlled detuning of the RF detection apparatus 100, in accordance with some embodiments of the disclosure.
  • RF receiver coil 1401 comprises a loop having inductor L and capacitor C pairs 1421.
  • the loop defines an RF signal collection area 1422, in accordance with some embodiments.
  • four pairs of L and C are shown. In each pair of L and C, L and C are coupled together in parallel.
  • a detuning circuit is integrated in the loop.
  • the detuning circuit comprises of active and/or passive devices.
  • the detuning circuit includes diode 1423 with an anode terminal coupled to one L and C pair and a cathode coupled to another L and C pair.
  • diode 1423 is controlled via a control signal.
  • the control signal provides RF protection to the sensitive receive electronics.
  • control signal detunes the coil by adding resistance.
  • control signal adds resistive loss to detune the high Q of the oscillator.
  • the chamber of MRI coils is pulsed with electromagnetic pulses (e.g., killo Watt pulses).
  • the anode and cathode of diode 1423 are also coupled to inductors which receive the input RF signal.
  • the detuning circuit controls the center frequency and/or the quality factor of the RF circuit.
  • the detuning circuit can be a MEMS (micro-electrical-mechanical-system) switch to enable high contrast switching with EMI (electromagnetic interference) resistance.
  • MEMS micro-electrical-mechanical-system
  • Balun 1402 couples to RF Rx 1401 and to LNA 1403.
  • Balun 1402 is illustrated as a common-mode choke that suppresses common mode noise due to DC signal or due to electromagnetic induction. For example, if RF Rx 1401 picks up unwanted charge, that unwanted charge is choked by Balun 1402.
  • Balun 1402 is implemented using mutual inductors Ll and L2 and/or solenoids.
  • LNA 1403 is coupled to Balun 1402 and STO apparatus 1404.
  • LNA 1403 amplifies the very weak signals captured by an antenna or RF Rx 1401 and provided to LNA 1403 via Balun 1402. Essentially, signals that are barely recognizable are amplified by LNA 1403 without adding a lot of noise.
  • LNA 1403 has a low Noise Figure (NF).
  • NF Noise Figure
  • LNA 1403 has a NF of ldB (decibel) and a high gain (e.g., 20dB).
  • STO apparatus 1404 receives the amplified RF signal from LNA 1403 and down converts it to IF signal with its built-in oscillator and mixer.
  • the IF signal is provided to DSP 1405. Any known suitable DSP may be used for implementing DSP 1405.
  • Fig. 15 illustrates an RF detection apparatus 1500 for a wireless receiver having the 3T STO with built-in Mixer, according to some embodiments of the disclosure.
  • RF Rx coil 1401 and Balun 1402 are removed and replaced with
  • Antenna 1501 may comprise one or more directional or omnidirectional antennas, including monopole antennas, dipole antennas, loop antennas, patch antennas, microstrip antennas, coplanar wave antennas, or other types of antennas suitable for transmission of RF signals.
  • Antenna(s) 1501 are separated to take advantage of spatial diversity.
  • Fig. 16 illustrates an apparatus 1600, with the 3T STO having built-in Mixer, showing parallel sensing using multiple receiver coils at a single frequency, according to some embodiments of the disclosure.
  • apparatus 1600 comprises a space division multiplexed signal array that includes antennas 1601 I-N, STOS 1 101 I-N, 1 102I- N, Isolators 1103 I-N, and filters 1602I-N.
  • antenna 16011 is coupled to STO 11011 which provides an RF output signal to Bias-T 11021.
  • the output of Bias-T 11021 is received by Isolator 11031 and then filtered by filter 1602i.
  • the output of filter 1602i is then processed by a DSP logic.
  • One reason for being able to form a parallel sensing apparatus 1600 is the small size of STO compared to transitional mixers with local oscillating clock sources. As such, many antennas with RF detection circuits (with STOs) can be used in a small form factor to detect and process data in parallel.
  • Fig. 17 illustrates an apparatus 1700, with the 3T STO having built-in Mixer, showing parallel sensing with frequency multiplexing, according to some embodiments of the disclosure.
  • FDM frequency division multiplexing
  • each STO operates at a different oscillation frequency.
  • STO 11011 operates at coi
  • STO 1 lOb operates at C02
  • STON operates at CON, where‘N’ is an integer greater than two.
  • the output of all STOs is a summation of RF signals with different frequencies.
  • each STO is tuned to operate at a different frequency
  • the same interconnect can be used to collect all RF signals output from the STOs.
  • the number of interconnects are reduced compared to apparatus 1600.
  • the frequency of each STO may be defined by the nature of the input RF signal. For example, for MRI, the center frequency is 64 MHz to 128 MHz, for cellular and adhoc wireless networks the center frequency is 500 MHz to 3 GHz, and for millimeter wave, the center frequency is 60 GHz. All these ranges are viable with STOs.
  • the RF signal’s carrier frequency is the same for each input but the center oscillating frequency of the STOs is different by n x oik.
  • the IF signal goes to a bandpass filter where the center frequency of the bandpass filter in the IF output after the isolator is n x oik.
  • the signal is reconstructed in the DSP (this is done to create a higher power receive signal and thus higher S/N ratio).
  • the STOs l lOh-N are tuned to the operating frequencies coi-Nvia the feedback provided from the DC bias and control to Bias-T 1102.
  • filters are used to detect the respective RF signal.
  • filters 1702I-N are centered at oik. 2 oik.3 oik. . . Non, where‘N’ is an integer greater than three.
  • the filters can be present on the device near the STOs or can be in a remote location (i.e., away from the STOs). Any suitable filter can be used for implementing filters 1702I-N.
  • Fig. 18 illustrates a sensing array 1800 formed with the apparatus of Fig. 16, according to some embodiments of the disclosure.
  • Sensing array 1800 applies the parallel sensing scheme of apparatus 1600.
  • an MxN array is formed with antennas of RF Rx coils 1801NM and STOs I I OINM tuned to a single frequency co, where‘M’ is the number of columns (e.g., 4) and‘N’ is the number of rows (e.g., 5).
  • each column of sensing array 1800 results in‘N’ number of wires that carry respective down converted RF (IF) signals for further processing.
  • sensing array 1800 generates MxN wires with MxN down converted IF signals for DSP logic 1405 to process.
  • the size of sensing array 1800 is small enough that it can fit in modem hand-held devices without having varacters and inductors, in accordance with some embodiments.
  • Fig. 19 illustrates a sensing array 1900 formed with the apparatus of Fig. 16, according to some embodiments of the disclosure.
  • Sensing array 1900 applies the parallel sensing scheme of apparatus 1800.
  • RF signal can be collected via‘M’ wires where each column is a frequency multiplexed arrangement of RF receivers.
  • sensing array 1900 has significantly fewer number of interconnects allowing for further reduction in the form factor of the arrays.
  • STO based RF detection described with reference to various embodiments allows for massively parallel RF detection comprising of detecting elements in excess of 1000 detectors. In comparison, the RF detection schemes used in the state of the art MRI is only limited to 24 channels.
  • the STO based RF detection of the various embodiments also improves signal collection times for sensing. Sensing time is approximately proportional to l/(number of channels).
  • the STO based RF detection of the various embodiments has a capability of being turned on the fly as required by the application or electromagnetic environment. For example, by adjusting the DC bias control to Bias-T 1102 and/or by adjusting the DC Bias-To SHE interconnect 222, operating frequency of the STO can be adjusted. Since the mixer and local oscillator functions are integrated in one device, the STO based RF detection of the various embodiments reduces the area of the RF detection scheme.
  • Fig. 20A illustrates an equivalent vector spin circuit 2000 for STO RF detector with locally generated oscillator, according to some embodiments of the disclosure.
  • STO 1101 can be modeled using vector spin circuit theory comprising a 4x4 conduction matrix formulation for spin transport coupled with magnetization dynamics, in accordance with some embodiments.
  • Model 2000 can be self-consistently coupled to the nano-magnet dynamics including the thermal stochastic noise effects, in accordance with some
  • the spin torque acting on the free layer in a spin-orbit torque MTJ originates from spin torque due to spin injection from the fixed layer, and from spin torque due to the spin orbit torque acting on the free layer.
  • the dynamics of the magnetic junction e.g., MTJ 521) are solved self-consistently with the spin transport in the equivalent circuit models.
  • the equivalent vector spin circuit for the magnetic junction (e.g., MTJ 521) comprises of the equivalent spin conductance of the fixed Ferromagnet (FMfixed) and free Ferromagnet (FMocc) interfaces to form the magnetic junction (e.g., MTJ 521).
  • the vector spin equivalent circuit model for MTJ 521 is in model 2000.
  • model 2000 comprises of three nodes NO, Nl and N2 to describe MTJ 521.
  • the RF input is applied to nodes 3 to 5 (or the low impedance configuration of Fig. 13.
  • the IF output is collected across nodes 5 and 0, in accordance with some embodiments.
  • the magnetization of the top fixed layer and the bottom free layer are described by rhf ix md in ⁇ ree .
  • the 4-component conductivity of the FM1 and oxide interface is described by GFMI and the conductivity of the FM2 and the oxide interface is described by GFM2.
  • the conductance matrix describing the spin transport across a FM/Oxide interface can be written as:
  • Gn is the interface conductivity (per interface) of the FM/MgO interface
  • a(V) is the spin polarization across the interface as a function of voltage
  • GSL(V C ) and GFL(V c ) are Slonczewski and field like torque contributions from the tunneling spin current across the interface.
  • the voltage dependence of spin polarization a(V), GSL(V), and GFL (V) is dependent on the detailed band structure of the electrodes and tunneling materials.
  • the effect of magnetization rotation for a precessing MTJ 521 can be described using the proposed model, where the 4 component conductance evolve as a function of the magnetization of the free magnet.
  • R(in) is a 4-component transformation to rotate the conductance matrices.
  • the spin torque from tunneling spin currents acting on the magnet and the effect of spin torque from spin orbit layer are included via a spin injection into the free layer as governed by the physics of spin injection from SHE layer 222 to FM layer.
  • the equivalent spin circuit model includes a current control spin current to model the injection of spin current from SHE 222 to the free magnet layer.
  • the field like component of spin orbit torque is also added via a current controlled effective magnetic field due to spin orbit torque.
  • Fig. 20B illustrates a plot 2020 showing tunability of the STO, according to some embodiments of the disclosure.
  • x-axis is Voltage (V) and y-axis is Frequency (GHz).
  • V Voltage
  • GHz Frequency
  • a simulation of the tunable spin torque dynamics of the SHE oscillator driven by the spin current response from a vector spin circuit model 2000 is shown by plot 2020.
  • the vector magnetization dynamics of the free layer showing tunability of the local oscillator due to the combined action of anti-damping spin torque and effective field due to spin orbit effects is shown in plot 2020.
  • An input RF signal centered at 10 GHz is shown in Fig. 12A, while the local oscillator dynamics are shown in the inset.
  • the output of the RF detector across nodes 5 and 0 is shown in Fig.
  • Figs. 12A-C The simulations of Figs. 12A-C assume a 70 kT magnet with dimensions of 20 X 60 nm and with spin orbit metallic electrode of 60 X 60 nm of resistivity 200 pm. cm. In this simulation example, the bulk spin hall ratio is 0.15 and the effective Rashaba field is 8 c 10 6 Oe/(A/cm 2 ) for the transient vector spin simulations.
  • Fig. 21A illustrates a cross-section 2100 of an oscillator having a magnetic junction 2121 with magnets having perpendicular magnetizations, where a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • the magnetic junction here is illustrated by reference sign 2121 where the layers under layer 22lb (e.g., dielectric or metal/metal-oxide) together form the structure comprising the free magnet of the junction.
  • the device of Fig. 21A is similar to the device of Fig. 5A except that the free magnets 52laa and 52lae are replaced with composite magnets having multiple layers.
  • the composite stack of multi-layer free magnet 2l2laa includes‘n’ layers of first material and second material.
  • the composite stack comprises layers 2l2laai- n and 2l2labi-n stacked in an alternating manner, where‘n’ has a range of 1 to 10.
  • the first material includes one of: Co, Ni, Fe, or an Heusler alloy.
  • the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
  • the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
  • the Heusler alloy includes one of: Cu 2 MnAl, Cu 2 MnIn, Cu 2 MnSn, NfMnAl, Ni 2 MnIn, Ni 2 MnSn, Ni 2 MnSb, Ni 2 MnGa Co 2 MnAl, Co 2 MnSi, Co 2 MnGa, Co 2 MnGe, Pd 2 MnAl, Pd 2 MnIn, Pd 2 MnSn, Pd 2 MnSb, Co 2 FeSi, Co 2 FeAl, Fe 2 VAl, Mn 2 VGa, Co 2 FeGe, MnGa, or MnGaRu.
  • the first material has a thickness tl in a range of 0.6 nm to 2 nm.
  • the second material has a thickness t2 in a range of 0.1 nm to 3 nm. While the embodiments here show first material being at the bottom followed by the second material, the order can be reversed without changing the technical effect.
  • composite stack of multi-layer free magnet 2l2lbb includes‘n’ layers of first material and second material.
  • the composite stack comprises layers 2l2laai- n and 2l2labi- n stacked in an alternating manner, where‘n’ has a range of 1 to 10.
  • the first material includes one of: Co, Ni, Fe, or a Heusler alloy.
  • the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
  • the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
  • the Heusler alloy includes one of: Cu 2 MnAl, Cu 2 MnIn, Cu 2 MnSn, Ni 2 MnAl, Ni 2 MnIn, Ni 2 MnSn, Ni 2 MnSb, Ni 2 MnGa Co 2 MnAl, Co 2 MnSi, Co 2 MnGa, Co 2 MnGe, Pd 2 MnAl, Pd 2 MnIn, Pd 2 MnSn, Pd 2 MnSb, Co 2 FeSi, Co 2 FeAl, Fe 2 VAl, Mn 2 VGa, Co 2 FeGe, MnGa, or MnGaRu.
  • the first material has a thickness tl in a range of 0.6 nm to 2 nm.
  • the second material has a thickness t2 in a range of 0.1 nm to 3 nm. While the embodiments here show first material being at the bottom followed by the second material, the order can be reversed without changing the technical effect.
  • magnetization for composite magnet 2l2laa is 1201 (e.g., +z or -z directions)
  • magnetization or composite magnet 2l2lbb is 1202 (e.g., +z or -z directions)
  • magnetization of fixed magnet 22 lc is 2103.
  • Figs. 5-9 can be mixed in any order.
  • the in-plane magnet 524 can be replaced with an AFM magnet
  • free magnet structure with free magnets and coupling layer can be replaced with a single magnet with free magnetization
  • in plane magnets can be replaced with perpendicular magnets.
  • the magnets (free and/or fixed) can also be paramagnets.
  • Fig. 21B illustrates a cross-section 2130 of a oscillator having a magnetic junction 2131 with magnets having perpendicular magnetizations, where a free magnet structure and a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • composite stack of multi-layer fixed magnet 2l2lcc includes‘n’ layers of first material and second material.
  • the composite stack comprises layers 2l2laai- n and 2l2labi- n stacked in an alternating manner, where‘n’ has a range of 1 to 10.
  • the first material includes one of: Co, Ni, Fe, or Heusler alloy.
  • the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
  • the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
  • the Heusler alloy includes one of: Cu 2 MnAl, CmMnln. CmMnSn. NfiMnAl, Ni 2 MnIn, Ni 2 MnSn, Ni 2 MnSb, Ni 2 MnGa Co 2 MnAl, Co 2 MnSi, Co 2 MnGa, Co 2 MnGe, Pd 2 MnAl, Pd 2 MnIn, Pd 2 MnSn, Pd 2 MnSb, Co 2 FeSi, Co 2 FeAl, Fe 2 VAl, Mn 2 VGa, Co 2 FeGe, MnGa, or MnGaRu.
  • the first material has a thickness t3 in a range of 0.6 nm to 2 nm.
  • the second material has a thickness t4 in a range of 0.1 nm to 3 nm. While the embodiments here show the first material being at the bottom followed by the second material, the order can be reversed without changing the technical effect.
  • Fig. 21C illustrates a cross-section 2150 of a oscillator having a magnetic junction 2151 with magnets having perpendicular magnetizations, where a fixed magnet structure and one of the free magnets of a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • free magnet 2l2lbb of Fig. 21C is replaced with a non-composite free magnet 521 ac.
  • the magnetic junction is labeled as 2151.
  • Fig. 21D illustrates a cross-section 2160 of a oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • free magnet 2121 aa of Fig. 21D is replaced with a non-composite free magnet 521 aa.
  • the magnetic junction is labeled as 2161.
  • Fig. 21E illustrates a cross-section 2170 of a oscillator having a magnetic junction 2171 with magnets having perpendicular magnetizations, where a fixed magnet structure and one of the free magnets of a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in- plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • free magnet 82laa of Fig. 21B is replaced with a non-composite free magnet 52laa.
  • the magnetic junction is labeled as 2171.
  • Fig. 21F illustrates a cross-section 2180 of a oscillator having a magnetic junction 2181 with magnets having perpendicular magnetizations, where a free magnet structure and a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet which is adjacent to an AFM embedded in the SOC interconnect, according to some embodiments of the disclosure.
  • the AFM 625 is removed from the magnetic via and integrated in the SOC interconnect 222 as layer 722.
  • Fig. 22 illustrates a flowchart 2200 of a method for forming an SOT or SOC based oscillator, in accordance with some embodiments. While the following blocks (or process operations) in the flowchart are arranged in a certain order, the order can be changed. In some embodiments, some blocks can be executed in parallel.
  • a first magnetic junction is formed.
  • a second magnetic junction is formed.
  • an interconnect is formed adjacent to the first and second magnetic junctions.
  • a first structure is formed adjacent to the interconnect such that the first structure is under the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device.
  • a second structure is formed adjacent to the interconnect such that the second structure is under the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the plane of the device.
  • the method of forming the interconnect comprises forming a first section and a section coupled to the first section via a conducting material.
  • the magnet of the first structure is adjacent to the first section, and wherein the magnet of the second structure is adjacent to the second section.
  • the first section or second section comprises an antiferromatic (AFM) material.
  • the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
  • the AFM material is a quasi-two-dimensional triangular AFM including Nip- x)M x Ga2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
  • the first section or second section comprises: one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b- W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth or elements of 3d, 4d, 5d and 4f, 5f periodic groups, Ti, S, W, Mo, Se, B, Sb, Re, La, C, P, La, As, Sc, O, Bi, Ga, Al, Y, In, Ce, Pr, Nd, F, Ir, Mn, Pd, or Fe.
  • b-Tantalum b-Ta
  • Ta b-Tungsten
  • W Platinum
  • Cu Copper
  • the first section or second section comprises: spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material.
  • the first section or section comprises: a spin orbit material which includes materials that exhibit Rashba-Bychkov effect.
  • the first or second magnetic junctions is one of a spin valve or a magnetic tunneling junction (MTJ).
  • the method of forming the first or second magnetic junctions include: forming a stack of structures includes: forming a first structure comprising a magnet with an unfixed perpendicular magnetic anisotropy (PMA), wherein the first structure has an anisotropy axis perpendicular to the plane of the device; forming a second structure comprising one of a dielectric or metal; forming a third structure comprising a magnet with fixed PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations are in-plane magnetizations.
  • PMA perpendicular magnetic anisotropy
  • the method of forming the first or second magnetic junctions include: forming a stack of structures including: forming a first structure comprising a magnet with an unfixed in-plane magnetic anisotropy, wherein the first structure has an anisotropy axis along the plane of the device; forming a second structure comprising one of a dielectric or metal; forming a third structure comprising a magnet with fixed in-plane magnetic anisotropy, wherein the third structure has an anisotropy axis along the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations have perpendicular magnetic anisotropy (PMA).
  • PMA perpendicular magnetic anisotropy
  • the method of forming the magnetic junction comprises: forming a fourth structure between the first and second structures, wherein the fourth structure includes one or more of: Ru, Os, Hs, or Fe. In some embodiments, the method of forming the magnetic junction comprises forming a fifth structure between the second and third structures, wherein the fifth structure includes one or more of: Ru, Os, Hs, or Fe. In some embodiments, the method of forming the first structure comprises forming an antiferromagnet (AFM) adjacent to the magnet of the first structure, and wherein the second structure comprises an AFM adjacent to the magnet of the second structure. In some embodiments, the fourth structure is between the interconnect and an eighth structure, wherein the eighth structure includes an antiferromagnet (AFM). In some embodiments, the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
  • the AFM material is a quasi-two-dimensional triangular AFM including Ni(i -X) M x Ga2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
  • the magnets of the first and/or second structures comprises one of: Co, Ni, Fe, or Heusler alloy.
  • the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
  • the method of forming the first and/or the third structures of the first and/or second magnetic junctions comprise forming a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy; and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
  • the method of forming the first and/or the third structures of the first and/or second magnetic junctions comprise forming a stack of three materials including a first material adjacent to the interconnect, a second material adjacent to the first material but not in contact with the interconnect, and third material adjacent to the second material and the second structure, wherein the first material includes one or more of: Co, Ni, Fe, or Heusler alloy, wherein the second material comprises Ru; and wherein the third material includes one or more of Co, Ni, Fe, or Heusler alloy.
  • Figs. 23A-B illustrate a 3D view 2300 and corresponding cross-section view 2330, respectively, of an oscillator having a magnetic junction with magnets having in-plane magnetizations, and a via having perpendicular magnet adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Figs. 23A-B is similar to Figs. 5A-B, respectively, but for different kinds of magnets.
  • magnetic junction 521 is replaced by magnetic junction 2351.
  • perpendicular free magnet 52laa is replaced with in-plane free magnet 232 laa
  • perpendicular free magnet 52 lab is replaced with in-plane free magnet 232 lab
  • perpendicular fixed magnet 52 lac is replaced with in-plane fixed magnet 232lac.
  • Further in-plane fixed magnet 534 is replaced by perpendicular fixed magnet 2334.
  • the devices of Figs. 23A-B are similar to devices of Figs. 5A-B.
  • Figs. 24A-B illustrate a 3D view 2400 and corresponding cross-section view 2430, respectively, of an oscillator having a magnetic junction with magnets having in-plane magnetizations, and a via comprising perpendicular magnet and an anti-ferromagnet (AFM) one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
  • Figs. 24A-B is similar to Figs. 6A-B, respectively, but for different kinds of magnets. For example, magnetic junction 521 is replaced by magnetic junction 2351.
  • perpendicular free magnet 52laa is replaced with in plane free magnet 2321 aa
  • perpendicular free magnet 521 ab is replaced with in-plane free magnet 232lab
  • perpendicular fixed magnet 52lac is replaced with in-plane fixed magnet 232 lac.
  • Further in-plane fixed magnet 534 is replaced by perpendicular fixed magnet 2334 which is coupled to AFM 625.
  • the devices of Figs. 24A-B are similar to devices of Figs. 5A-B.
  • Fig. 25 illustrates a smart device or a computer system or a SoC (System-on- Chip) 2300 with an SOT or SOC based oscillator, according to some embodiments of the disclosure.
  • SoC System-on- Chip
  • the transistors in various circuits and logic blocks described here are metal oxide semiconductor (MOS) transistors or their derivatives, where the MOS transistors include drain, source, gate, and bulk terminals.
  • the transistors and/or the MOS transistor derivatives also include Tri-Gate and FinFET transistors, Gate All Around Cylindrical Transistors, Tunneling FET (TFET), Square Wire, or Rectangular Ribbon Transistors, ferroelectric FET (FeFETs), or other devices implementing transistor functionality like carbon nanotubes or spintronic devices.
  • MOSFET symmetrical source and drain terminals i.e., are identical terminals and are interchangeably used here.
  • a TFET device on the other hand, has asymmetric Source and Drain terminals.
  • BJT PNP/NPN Bi-polar junction transistors
  • BiCMOS BiCMOS
  • CMOS complementary metal oxide semiconductor
  • Fig. 25 illustrates a block diagram of an embodiment of a mobile device in which flat surface interface connectors could be used.
  • computing device 1600 represents a mobile computing device, such as a computing tablet, a mobile phone or smart-phone, a wireless-enabled e-reader, or other wireless mobile device. It will be understood that certain components are shown generally, and not all components of such a device are shown in computing device 2300.
  • computing device 2300 includes first processor 2310 with an SOT or SOC based oscillator, according to some embodiments discussed.
  • Other blocks of the computing device 2300 may also include an SOT or SOC based oscillator, according to some embodiments.
  • the various embodiments of the present disclosure may also comprise a network interface within 2370 such as a wireless interface so that a system embodiment may be incorporated into a wireless device, for example, cell phone or personal digital assistant.
  • processor 2310 can include one or more physical devices, such as microprocessors, application processors,
  • microcontrollers programmable logic devices, or other processing means.
  • the processing operations performed by processor 2310 include the execution of an operating platform or operating system on which applications and/or device functions are executed.
  • the processing operations include operations related to I/O (input/output) with a human user or with other devices, operations related to power management, and/or operations related to connecting the computing device 2300 to another device.
  • the processing operations may also include operations related to audio I/O and/or display I/O.
  • computing device 2300 includes audio subsystem 2320, which represents hardware (e.g., audio hardware and audio circuits) and software (e.g., drivers, codecs) components associated with providing audio functions to the computing device. Audio functions can include speaker and/or headphone output, as well as microphone input. Devices for such functions can be integrated into computing device 2300, or connected to the computing device 2300. In one embodiment, a user interacts with the computing device 2300 by providing audio commands that are received and processed by processor 2310.
  • audio subsystem 2320 represents hardware (e.g., audio hardware and audio circuits) and software (e.g., drivers, codecs) components associated with providing audio functions to the computing device. Audio functions can include speaker and/or headphone output, as well as microphone input. Devices for such functions can be integrated into computing device 2300, or connected to the computing device 2300. In one embodiment, a user interacts with the computing device 2300 by providing audio commands that are received and processed by processor 2310.
  • computing device 2300 comprises display subsystem 2330.
  • Display subsystem 2330 represents hardware (e.g., display devices) and software (e.g., drivers) components that provide a visual and/or tactile display for a user to interact with the computing device 2300.
  • Display subsystem 2330 includes display interface 2332, which includes the particular screen or hardware device used to provide a display to a user.
  • display interface 2332 includes logic separate from processor 2310 to perform at least some processing related to the display.
  • display subsystem 2330 includes a touch screen (or touch pad) device that provides both output and input to a user.
  • computing device 2300 comprises I/O controller 2340.
  • I/O controller 2340 represents hardware devices and software components related to interaction with a user.
  • I/O controller 2340 is operable to manage hardware that is part of audio subsystem 2320 and/or display subsystem 2330.
  • I/O controller 2340 illustrates a connection point for additional devices that connect to computing device 2300 through which a user might interact with the system.
  • devices that can be attached to the computing device 2300 might include microphone devices, speaker or stereo systems, video systems or other display devices, keyboard or keypad devices, or other I/O devices for use with specific applications such as card readers or other devices.
  • I/O controller 2340 can interact with audio subsystem 2320 and/or display subsystem 2330.
  • input through a microphone or other audio device can provide input or commands for one or more applications or functions of the computing device 2300.
  • audio output can be provided instead of, or in addition to display output.
  • display subsystem 2330 includes a touch screen
  • the display device also acts as an input device, which can be at least partially managed by I/O controller 2340.
  • I/O controller 2340 manages devices such as accelerometers, cameras, light sensors or other environmental sensors, or other hardware that can be included in the computing device 2300.
  • the input can be part of direct user interaction, as well as providing environmental input to the system to influence its operations (such as filtering for noise, adjusting displays for brightness detection, applying a flash for a camera, or other features).
  • computing device 2300 includes power management 2350 that manages battery power usage, charging of the battery, and features related to power saving operation.
  • Memory subsystem 2360 includes memory devices for storing information in computing device 2300. Memory can include nonvolatile (state does not change if power to the memory device is interrupted) and/or volatile (state is indeterminate if power to the memory device is interrupted) memory devices. Memory subsystem 2360 can store application data, user data, music, photos, documents, or other data, as well as system data (whether long-term or temporary) related to the execution of the applications and functions of the computing device 2300.
  • Elements of embodiments are also provided as a machine-readable medium (e.g., memory 2360) for storing the computer-executable instructions (e.g., instructions to implement any other processes discussed herein).
  • the machine-readable medium e.g., memory 2360
  • embodiments of the disclosure may be downloaded as a computer program (e.g., BIOS) which may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals via a communication link (e.g., a modem or network connection).
  • BIOS a computer program
  • a remote computer e.g., a server
  • a requesting computer e.g., a client
  • a communication link e.g., a modem or network connection
  • computing device 2300 comprises connectivity 2370.
  • Connectivity 2370 includes hardware devices (e.g., wireless and/or wired connectors and communication hardware) and software components (e.g., drivers, protocol stacks) to enable the computing device 2300 to communicate with external devices.
  • the computing device 2300 could be separate devices, such as other computing devices, wireless access points or base stations, as well as peripherals such as headsets, printers, or other devices.
  • Connectivity 2370 can include multiple different types of connectivity.
  • the computing device 2300 is illustrated with cellular connectivity 2372 and wireless connectivity 2374.
  • Cellular connectivity 2372 refers generally to cellular network connectivity provided by wireless carriers, such as provided via GSM (global system for mobile communications) or variations or derivatives, CDMA (code division multiple access) or variations or derivatives, TDM (time division multiplexing) or variations or derivatives, or other cellular service standards.
  • Wireless connectivity (or wireless interface) 2374 refers to wireless connectivity that is not cellular, and can include personal area networks (such as Bluetooth, Near Field, etc.), local area networks (such as Wi-Fi), and/or wide area networks (such as WiMax), or other wireless communication.
  • computing device 2300 comprises peripheral connections 2380.
  • Peripheral connections 2380 include hardware interfaces and connectors, as well as software components (e.g., drivers, protocol stacks) to make peripheral connections. It will be understood that the computing device 2300 could both be a peripheral device ("to" 2382) to other computing devices, as well as have peripheral devices ("from” 2384) connected to it.
  • the computing device 2300 commonly has a "docking" connector to connect to other computing devices for purposes such as managing (e.g., downloading and/or uploading, changing, synchronizing) content on computing device 2300. Additionally, a docking connector can allow computing device 2300 to connect to certain peripherals that allow the computing device 2300 to control content output, for example, to audiovisual or other systems.
  • the computing device 2300 can make peripheral connections 2380 via common or standards-based connectors.
  • Common types can include a Universal Serial Bus (USB) connector (which can include any of a number of different hardware interfaces), DisplayPort including MiniDisplayPort (MDP), High Definition Multimedia Interface (HDMI), Firewire, or other types.
  • USB Universal Serial Bus
  • MDP MiniDisplayPort
  • HDMI High Definition Multimedia Interface
  • Firewire or other types.
  • Example 1 An apparatus comprising: a first magnetic junction; a second magnetic junction; an interconnect adjacent to the first and second magnetic junctions; a first structure adjacent to the interconnect such that the first structure is under the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device; and a second structure adjacent to the interconnect such that the second structure is under the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the plane of the device.
  • Example 2 The apparatus of example 1, wherein the interconnect comprises a first section and a section coupled to the first section via a conducting material.
  • Example 3 The apparatus of example 2, wherein the magnet of the first structure is adjacent to the first section, and wherein the magnet of the second structure is adjacent to the second section.
  • Example 4 The apparatus of example 2, wherein the first section or second section comprises an antiferromatic (AFM) material.
  • AFM antiferromatic
  • Example 5 The apparatus of example 4, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
  • Example 6 The apparatus of example 4, wherein the AFM material is a quasi- two-dimensional triangular AFM including Ni(i- X) M x Ga2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
  • Example 7 The apparatus of example 2, wherein the first section or second section comprises: one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b-W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth or elements of 3d, 4d, 5d and 4f, 5f periodic groups, Ti, S, W, Mo, Se, B, Sb, Re, La, C, P, La, As, Sc, O, Bi,
  • Example 8 The apparatus of example 2, wherein the first section or second section comprises: spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material.
  • Example 9 The apparatus of example 2, wherein the first section or second section comprises: a spin orbit material which includes materials that exhibit Rashba- Bychkov effect.
  • Example 10 The apparatus according to any one of preceding examples, wherein the first or second magnetic junctions is one of a spin valve or a magnetic tunneling junction (MTJ).
  • MTJ magnetic tunneling junction
  • Example 11 The apparatus according to any one of examples 1 to 8, wherein the first or second magnetic junctions include: a stack of structures including: a first structure comprising a magnet with an unfixed perpendicular magnetic anisotropy (PMA) relative to the plane of the device; a second structure comprising one of a dielectric or metal; and a third structure comprising a magnet with fixed PMA relative to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations are in plane magnetizations.
  • PMA perpendicular magnetic anisotropy
  • Example 12 The apparatus according to any one of examples 1 to 8, wherein the first or second magnetic junctions include: a stack of structures including: a first structure comprising a magnet with an unfixed in-plane magnetic anisotropy relative to the plane of the device; a second structure comprising one of a dielectric or metal; a third structure comprising a magnet with fixed in-plane magnetic anisotropy relative to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations have perpendicular magnetic anisotropy (PMA).
  • PMA perpendicular magnetic anisotropy
  • Example 13 The apparatus of examples 11 or 12, wherein the magnetic junction comprises: a fourth structure between the first and second structures, wherein the fourth structure includes one or more of: Ru, Os, Hs, or Fe.
  • Example 14 The apparatus of examples 11 or 12, wherein the magnetic junction comprises a fifth structure between the second and third structures, wherein the fifth structure includes one or more of: Ru, Os, Hs, or Fe.
  • Example 15 The apparatus of example 2, wherein the first structure comprises an antiferromagnet (AFM) adjacent to the magnet of the first structure, and wherein the second structure comprises an AFM adjacent to the magnet of the second structure.
  • AFM antiferromagnet
  • Example 16 The apparatus of example 2, wherein the fourth structure is between the interconnect and an eighth structure, wherein the eighth structure includes an antiferromagnet (AFM).
  • AFM antiferromagnet
  • Example 17 The apparatus of examples 15 or 16, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
  • Example 18 The apparatus of examples 15 or 16, wherein the AFM material is a quasi-two-dimensional triangular AFM including Ni(i- X) M x Ga2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
  • Example 19 The apparatus of example 1, wherein the magnets of the first and/or second structures comprises one of: Co, Ni, Fe, or Heusler alloy.
  • Example 20 The apparatus of example 19, wherein the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
  • Example 21 The apparatus of examples 11 or 12, wherein the first and/or the third structures of the first and/or second magnetic junctions comprise a super lattice including a first material and a second material, wherein the first material includes one of:
  • Co, Ni, Fe, or Heusler alloy wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
  • Example 22 The apparatus examples 11 or 12, wherein the first and/or the third structures of the first and/or second magnetic junctions comprise a stack of three materials including a first material adjacent to the interconnect, a second material adjacent to the first material but not in contact with the interconnect, and third material adjacent to the second material and the second structure, wherein the first material includes one or more of: Co, Ni, Fe, or Heusler alloy, wherein the second material comprises Ru; and wherein the third material includes one or more of Co, Ni, Fe, or Heusler alloy.
  • Example 23 A system comprising: a memory; a processor coupled to the memory, the processor having a spin wave switch, which comprises an apparatus according to any one of apparatus examples 1 to 22; and a wireless interface to allow the processor to communicate with another device.
  • Example 24 An apparatus comprising: an oscillator comprising an apparatus according to any one of examples 1 to 22; and circuitry to receive an output of the oscillator.
  • Example 25 An apparatus comprising: an array of antennas; and an array of oscillators with built-in mixers, wherein each antenna of the array of antennas is coupled to an oscillator forming a pair, wherein an individual oscillator comprises a spin orbit coupling material adjacent to a magnetic junction, and wherein at least one pair has an associated interconnect coupled to a corresponding Bias-T network.
  • Example 26 The apparatus of example 25, wherein at least one oscillator is to provide an oscillating output independent of an oscillating clock input.
  • Example 27 The apparatus of example 25 comprises: an array of isolators, wherein an individual isolator is coupled to the corresponding Bias-T network; and an array of filters, wherein an individual filter of the array of filters is coupled to the individual isolator of the array of isolators.
  • Example 28 The apparatus of example 25, wherein the array of antennas and the array of oscillators are configured as a space division multiplexed signal array.
  • Example 29 The apparatus of example 25, wherein the oscillator is according to any one of claims 1 to 22.
  • Example 30 An apparatus comprising: a parallel radio-frequency (RF) sensing array with a plurality of antennas, wherein an individual antenna is coupled to an oscillator according to any one apparatus examples 1 to 22.
  • RF radio-frequency
  • Example 31 A method comprising: forming a first magnetic junction
  • forming a second magnetic junction forming an interconnect adjacent to the first and second magnetic junctions; forming a first structure adjacent to the interconnect such that the first structure is under the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device; and forming a second structure adjacent to the interconnect such that the second structure is under the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the plane of the device.
  • Example 32 The method of example 31, wherein forming the interconnect comprises forming a first section and a section coupled to the first section via a conducting material.
  • Example 33 The method of example 32, wherein the magnet of the first structure is adjacent to the first section, and wherein the magnet of the second structure is adjacent to the second section.
  • Example 34 The method of example 32, wherein the first section or second section comprises an antiferromatic (AFM) material.
  • AFM antiferromatic
  • Example 36 The method of example 34, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
  • Example 37 The method of example 34, wherein the AFM material is a quasi-two-dimensional triangular AFM including Ni(i- X) M x Ga2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
  • Example 38 The method of example 32, wherein the first section or second section comprises: one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b-W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth or elements of 3d, 4d, 5d and 4f, 5f periodic groups, Ti, S, W, Mo, Se, B, Sb, Re, La, C, P, La, As, Sc, O, Bi,
  • Example 39 The method of example 32, wherein the first section or second section comprises: spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material.
  • Example 40 The method of example 32, wherein the first section or section comprises: a spin orbit material which includes materials that exhibit Rashba-Bychkov effect.
  • Example 41 The method according to any one of preceding method examples, wherein the first or second magnetic junctions is one of a spin valve or a magnetic tunneling junction (MTJ).
  • the first or second magnetic junctions is one of a spin valve or a magnetic tunneling junction (MTJ).
  • Example 42 The method according to any one of examples 31 to 38, wherein forming the first or second magnetic junctions include: forming a stack of structures including: forming a first structure comprising a magnet with an unfixed perpendicular magnetic anisotropy (PMA), wherein the first structure has an anisotropy axis perpendicular to the plane of the device; forming a second structure comprising one of a dielectric or metal; forming a third structure comprising a magnet with fixed PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations are in-plane magnetizations.
  • PMA perpendicular magnetic anisotropy
  • Example 42 The method according to any one of examples 31 to 38, wherein forming the first or second magnetic junctions include: forming a stack of structures including: forming a first structure comprising a magnet with an unfixed in-plane magnetic anisotropy, wherein the first structure has an anisotropy axis along the plane of the device; forming a second structure comprising one of a dielectric or metal; forming a third structure comprising a magnet with fixed in-plane magnetic anisotropy, wherein the third structure has an anisotropy axis along the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations have perpendicular magnetic anisotropy (PMA).
  • PMA perpendicular magnetic anisotropy
  • Example 43 The method of examples 41 or 42, wherein forming the magnetic junction comprises: forming a fourth structure between the first and second structures, wherein the fourth structure includes one or more of: Ru, Os, Hs, or Fe.
  • Example 44 The method of examples 41 or 42, wherein forming the magnetic junction comprises forming a fifth structure between the second and third structures, wherein the fifth structure includes one or more of: Ru, Os, Hs, or Fe.
  • Example 45 The method of example 31, wherein forming the first structure comprises forming an antiferromagnet (AFM) adjacent to the magnet of the first structure, and wherein the second structure comprises an AFM adjacent to the magnet of the second structure.
  • AFM antiferromagnet
  • Example 46 The method of example 31, wherein the fourth structure is between the interconnect and an eighth structure, wherein the eighth structure includes an antiferromagnet (AFM).
  • AFM antiferromagnet
  • Example 47 The method of examples 45 or 46, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
  • Example 48 The method of claims 45 or 46, wherein the AFM material is a quasi-two-dimensional triangular AFM including Ni(i- X) M x Ga2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
  • Example 49 The method of example 31, wherein the magnets of the first and/or second structures comprises one of: Co, Ni, Fe, or Heusler alloy.
  • Example 50 The method of example 49, wherein the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
  • Example 51 The method of examples 41 or 42, wherein forming the first and/or the third structures of the first and/or second magnetic junctions comprise forming a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy; and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
  • Example 52 The method of examples 41 or 42, wherein forming the first and/or the third structures of the first and/or second magnetic junctions comprise forming a stack of three materials including a first material adjacent to the interconnect, a second material adjacent to the first material but not in contact with the interconnect, and third material adjacent to the second material and the second structure, wherein the first material includes one or more of: Co, Ni, Fe, or Heusler alloy, wherein the second material comprises Ru; and wherein the third material includes one or more of Co, Ni, Fe, or Heusler alloy.

Abstract

An apparatus is provided which comprises: a first magnetic junction; a second magnetic junction; an interconnect adjacent to the first and second magnetic junctions; a first structure adjacent to the interconnect such that the first structure is adjacent to the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device; and a second structure adjacent to the interconnect such that the second structure is adjacent the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the x-y plane of the device.

Description

SPIN ORBIT COUPLING BASED OSCILLATOR USING EXCHANGE BIAS
BACKGROUND
[0001] Embedded memory with state retention can enable energy and computational efficiency. However, leading spintronic memory options, for example, spin transfer torque based magnetic random access memory (STT-MRAM), suffer from the problem of high voltage and high write current during the programming (e.g., writing) of a bit-cell. For instance, large write current (e.g., greater than 100 mA) and voltage (e.g., greater than 0.7 V) are required to write a tunnel junction based magnetic tunnel junction (MTJ). Limited write current also leads to high write error rates or slow switching times (e.g., exceeding 20 ns) in MTJ based MRAM. The presence of a large current flowing through a tunnel barrier leads to reliability issues in magnetic tunnel junctions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] The embodiments of the disclosure will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the disclosure, which, however, should not be taken to limit the disclosure to the specific embodiments, but are for explanation and understanding only.
[0003] Fig. 1A illustrates a magnetization response to an applied magnetic field for a ferromagnet.
[0004] Fig. IB illustrates a magnetization response to an applied magnetic field for a paramagnet.
[0005] Figs. 2A-B illustrate a three-dimensional (3D) view and corresponding top view, respectively, of a device having an out-of-plane magnetic tunnel junction (MTJ) stack coupled to a spin orbit coupling (SOC) interconnect.
[0006] Fig. 3 illustrates a cross-section of the SOC interconnect with electrons having their spins polarized in-plane and deflected up and down resulting from a flow of charge current.
[0007] Fig. 4A illustrates a plot showing write energy-delay conditions for one transistor and one MTJ with spin Hall effect (SHE) material compared to traditional MTJs.
[0008] Fig. 4B illustrates a plot comparing reliable write times for spin Hall MRAM and spin torque MRAM.
[0009] Figs. 5A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, and a via having an in-plane magnet adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0010] Figs. 6A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, and a via comprising an in-plane magnet and an anti-ferromagnet (AFM) one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0011] Figs. 7A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where an AFM is embedded in the SOC interconnect, and a via comprising an in-plane magnet which is adjacent to the AFM, according to some embodiments of the disclosure.
[0012] Figs. 8A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where an AFM electrode replaces the SOC interconnect, and where the oscillator further comprises a via including an in-plane magnet which is adjacent to the AFM, according to some embodiments of the disclosure.
[0013] Fig. 9 illustrates a cross-section of a cascaded SOC oscillators with charge based coupling between the SOC interconnects, which produces a charge based spin current excitation, in accordance with some embodiments.
[0014] Fig. 10 illustrates a scheme of an oscillatory Cellular Neural Network (CNN) that uses the SOC based oscillators, according to some embodiments.
[0015] Figs. 11A-B illustrate a three terminal (3T) high input impedance Spin Torque
Oscillator (STO) or SOC oscillator with built-in Mixer, according to some embodiments of the disclosure.
[0016] Fig. 12A illustrates a plot showing a single-sided amplitude spectrum of an input Radio Frequency (RF) signal which is input to the 3T STO with built-in Mixer, according to some embodiments of the disclosure.
[0017] Fig. 12B illustrates a plot showing magnetization oscillation produced by the
3T STO with built-in Mixer, according to some embodiments of the disclosure.
[0018] Fig. 12C illustrates a plot showing a single-sided amplitude spectrum of the output of the 3T STO with built-in Mixer, according to some embodiments of the disclosure.
[0019] Fig. 13A-B illustrate a 3T low input impedance STO or SOC oscillator with built-in Mixer, according to some embodiments of the disclosure. [0020] Fig. 14 illustrates an RF detection apparatus for Magnetic Resonance Imaging
(MRI) having the 3T STO with built-in Mixer, according to some embodiments of the disclosure, according to some embodiments of the disclosure.
[0021] Fig. 15 illustrates an RF detection apparatus for a wireless receiver having the
3T STO with built-in Mixer, according to some embodiments of the disclosure.
[0022] Fig. 16 illustrates an apparatus, with the 3T STO having built-in Mixer, showing parallel sensing using multiple receiver coils at a single frequency, according to some embodiments of the disclosure.
[0023] Fig. 17 illustrates an apparatus, with the 3T STO having built-in Mixer, showing parallel sensing with frequency multiplexing, according to some embodiments of the disclosure.
[0024] Fig. 18 illustrates a sensing array formed with the apparatus of Fig. 16, according to some embodiments of the disclosure.
[0025] Fig. 19 illustrates a sensing array formed with the apparatus of Fig. 16, according to some embodiments of the disclosure.
[0026] Fig. 20A illustrates an equivalent vector spin circuit for STO RF detector with locally generated oscillator, according to some embodiments of the disclosure.
[0027] Fig. 20B illustrates a plot showing tunability of the STO, according to some embodiments of the disclosure.
[0028] Fig. 21A illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0029] Fig. 21B illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a free magnet structure and a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0030] Fig. 21C illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a fixed magnet structure and one of the free magnets of a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0031] Fig. 21D illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0032] Fig. 21E illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a fixed magnet structure and one of the free magnets of a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0033] Fig. 21F illustrates a cross-section of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a free magnet structure and a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet which is adjacent to an AFM embedded in the SOC interconnect, according to some embodiments of the disclosure.
[0034] Fig. 22 illustrates a flowchart of a method for forming an SOT or SOC based oscillator, in accordance with some embodiments.
[0035] Figs. 23A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having in-plane magnetizations, and a via having perpendicular magnet adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0036] Figs. 24A-B illustrate a 3D view and corresponding cross-section view, respectively, of an oscillator having a magnetic junction with magnets having in-plane magnetizations, and a via comprising perpendicular magnet and an anti-ferromagnet (AFM) one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[0037] Fig. 25 illustrates a smart device or a computer system or a SoC (System-on-
Chip) with an SOT or SOC based oscillator, according to some embodiments of the disclosure. DETAILED DESCRIPTION
[0038] Detection and processing of Radio Frequency (RF) signals at a frontend of a receiver, which is part of a signal chain, is used in RF signal processing. Applications such as Global Positioning System (GPS), Magnetic Resonance Imaging (MRI), and highly attenuated signal receivers can benefit from highly parallel signal acquisitions. However, current RF detection and processing schemes use non-linear multipliers using RF electronics for down conversion of the RF signal to an intermediate frequency (IF) signal. The down conversion is generally performed by a mixer circuit that receives a local oscillating signal. This local oscillating signal is generated by a local oscillator (i.e.., a clock source) such as a phase locked loop (PLL).
[0039] This clock source for up or down frequency conversion may be generated off- chip or by an off-the instrument. For example, MRI apparatus has an off-chip clock source used for up or down conversion of RF input signals. Continuing with the MRI apparatus example, one reason for having a dedicated off-chip clock source is that available clock signals used by the MRI apparatus have frequencies not suitable for down conversion. Also, the number of available channels are limited in existing RF receivers (e.g., 10 to 20 channels), which increases the complexity of implementing highly parallel sensing.
[0040] In some embodiments, a spin torque oscillator (STO) or spin orbit coupling
(SOC) oscillator is described which is a multi-terminal device (e.g., a three terminal (3T) device or a five terminal (5T) device). In some embodiments, the STO is a self-sustained oscillator that operates via injection of spin current from a spin orbit torque electrode or a spin orbit coupling electrode. In some embodiments, the STO operates via a transverse exchange bias from a bottom electrode (e.g., a spin orbit torque electrode or a spin orbit coupling electrode). In some embodiments, the STO operates via spin injection from a magnetic junction (e.g., spin valve or magnetic tunneling junction (MTJ)) to produce magnetic oscillators in the free magnet layer of the magnetic junction.
[0041] The term“free” or“unfixed” here with reference to a magnet refers to a magnet whose magnetization direction can change along its easy axis upon application of an external field or force (e.g., Oersted field, spin torque, etc.). Conversely, the term“fixed” or “pinned” here with reference to a magnet refers to a magnet whose magnetization direction is pinned or fixed along an axis and which may not change due to application of an external field (e.g., electrical field, Oersted field, spin torque,).
[0042] Here, perpendicularly magnetized magnet (or perpendicular magnet, or magnet with perpendicular magnetic anisotropy (PMA)) refers to a magnet having a magnetization which is substantially perpendicular to a plane of the magnet or a device. For example, a magnet with a magnetization which is in a z-direction in a range of 90 (or 270) degrees +/- 20 degrees relative to an x-y plane of a device.
[0043] Here, an in-plane magnet refers to a magnet that has magnetization in a direction substantially along the plane of the magnet. For example, a magnet with a magnetization which is in an x or y direction and is in a range of 0 (or 180 degrees) +/- 20 degrees relative to an x-y plane of a device.
[0044] The term“device” may generally refer to an apparatus according to the context of the usage of that term. For example, a device may refer to a stack of layers or structures, a single structure or layer, a connection of various structures having active and/or passive elements, etc. Generally a device is a three dimensional structure with a plane along the x-y direction and a height along the z direction of an x-y-z Cartesian coordinate system. The plane of the device may also be the plane of an apparatus which comprises the device.
[0045] In some embodiments, spin Hall current (e.g., IsH-controi) interacts with the free magnet layer (or structure) to produce self-sustained oscillations/excitations. In some embodiments, a second tunneling excitation current (Isense-controi) interacts with an in-plane or perpendicularly polarized free magnet layer to produce or ensure self-sustained oscillations. In some embodiments, the path through the magnetic junction provides a sensing path generating an AC current at the oscillation frequency. In some embodiments, the path through the spin Hall electrode provides a path to connect spin Hall oscillators for coupling the state of the oscillators.
[0046] In some embodiments, a STO is formed from a single magnetic junction coupled to a spin orbit coupling electrode. In some embodiments, the STO or SOC oscillator comprises an antiferromagnetic (AFM) spin orbit coupling electrode with exchange bias experiencing spin excitation from a magnetic junction and/or SOC electrode or layer. In some embodiments, the SOC oscillator comprises a heavy metal SOC layer with exchange bias in-plane magnet experiencing spin excitation from magnetic junction and/or SOC layer.
[0047] In some embodiments, the STO is formed from cascaded magnetic junction devices (e.g., SOC electrode of one device is serially coupled to an SOC electrode of another device). In some embodiments, SOC oscillators are formed with in-plane magnets and in plane polarizing layers. In some embodiments, SOC oscillators are formed with free magnet(s) having perpendicular magnetic anisotropy (PMA) and PMA polarizing layers. In some embodiments, SOC oscillators are formed with PMA free magnet and in-plane fixed layer of the magnetic junction. In some embodiments, the SOC oscillator is formed with in- plane free magnet and PMA fixed magnet. In some embodiments, the SOC oscillator is formed from a magnetic junction in the absence of spin injection. In some embodiments, the SOC based oscillator uses exchange bias along the hard axis of the magnetic junction magnets.
[0048] Some embodiments describe a SOC based oscillator that comprises a magnetic under-layer via for dipole and exchange coupling. In some embodiments, the device comprises a perpendicular magnet in contact with an SOC write electrode (e.g., spin Hall effect write electrode) and a magnetic via to produce dipole/exchange bias fields. In some embodiments, in-plane exchange bias from an AFM and/or an in-plane fixed magnet is used to template the magnetic orientation of the free magnets of the magnetic junction. As such, the free magnets of the magnetic junction provide a strong effective in-plane magnet effect.
In some embodiments, both an in-plane fixed magnet and an AFM are formed in a via which is coupled to or adjacent to a surface of the SOC electrode such that the magnetic junction is formed on the other surface of the SOC electrode.
[0049] In some embodiments, the SOC electrode comprises an AFM. In one such embodiment, the via comprises a magnet with fixed in-plane magnetization. Since the AFM effect is provided by the SOC electrode in this example, an additional AFM may not be formed in the via. In some embodiments, the in-plane fixed magnet under the SOC electrode has a length longer than a length of the magnetic junction. Here, a length refers to a distance along ay-axis as described with reference to various figures. In some embodiments, the in plane magnet is made thick enough so that it is stable. Here, stability generally refers to the permanency of the magnetization direction. An unstable magnet in this example would be one that switches its magnetization upon application of an external field. In some embodiments, the AFM comprises Ir and Mn (or any other AFM) which can template the magnetic orientation of the in-plane magnet in the via.
[0050] In some embodiments, the free magnet structure of the magnetic junction comprises at least two free magnets that are coupled by a coupling layer. In some embodiments, the coupling layer comprises one or more of: Ru, Os, Hs, Fe, or other similar transition metals from the platinum group of the periodic table. In some embodiments, the coupling layer(s) are removed so that the free magnets of the free magnet structure or stack are directly connected with one another forming a single magnet (or a composite magnet).
[0051] In some embodiments, one or more of the free magnets of the free magnet structure of the magnetic junction comprises a composite magnet. The composite magnet may be a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy, and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the fixed magnet of the magnetic junction also comprises a composite magnet.
[0052] Some embodiments describe a STO or SOC oscillator based radio frequency
(RF) detection scheme. In some embodiments, the RF detector includes an STO with an integrated mixer (e.g., built-in mixer) and formed using a magnetic junction and a spin orbit coupling layer (e.g., a layer that exhibits spin Hall effect). In some embodiments, the RF detector is a multiplier that naturally provides a local clock demodulation frequency via inherent precessional dynamics of nanomagnets. In some embodiments, the 3T STO configuration is used to down convert the input RF signal to a corresponding base band as set by the local STO.
[0053] There are many technical effects/benefits of the various embodiments. For example, no special clock source is needed to down convert an RF signal to an IF signal. The size of the 3T (three terminal) STO with built-in Mixer of the various embodiments is much smaller than traditional mixers with local oscillators (LOs). As such, parallel sensing arrays with small form factor can be formed using the STOs of the various embodiments. The parallel sensing arrays using the STOs of the various embodiments allow for large number of parallel oscillators for increased signal collection (e.g., greater than 1000 channels). Other technical effects will be evident from the various embodiments and figures.
[0054] In the following description, numerous details are discussed to provide a more thorough explanation of embodiments of the present disclosure. It will be apparent, however, to one skilled in the art, that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring embodiments of the present disclosure.
[0055] Note that in the corresponding drawings of the embodiments, signals are represented with lines. Some lines may be thicker, to indicate more constituent signal paths, and/or have arrows at one or more ends, to indicate primary information flow direction. Such indications are not intended to be limiting. Rather, the lines are used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit or a logical unit. Any represented signal, as dictated by design needs or preferences, may actually comprise one or more signals that may travel in either direction and may be implemented with any suitable type of signal scheme. [0056] Throughout the specification, and in the claims, the term "connected" means a direct connection, such as electrical, mechanical, or magnetic connection between the things that are connected, without any intermediary devices.
[0057] The term "coupled" means a direct or indirect connection, such as a direct electrical, mechanical, or magnetic connection between the things that are connected or an indirect connection, through one or more passive or active intermediary devices.
[0058] The term“adjacent” here generally refers to a position of a thing being next to
(e.g., immediately next to or close to with one or more things between them) or adjoining another thing (e.g., abutting it).
[0059] The term "circuit" or“module” may refer to one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function.
[0060] The term "signal" may refer to at least one current signal, voltage signal, magnetic signal, or data/clock signal. The meaning of "a," "an," and "the" include plural references. The meaning of "in" includes "in" and "on."
[0061] The term“scaling” generally refers to converting a design (schematic and layout) from one process technology to another process technology and subsequently being reduced in layout area. The term“scaling” generally also refers to downsizing layout and devices within the same technology node. The term“scaling” may also refer to adjusting (e.g., slowing down or speeding up - i.e. scaling down, or scaling up respectively) of a signal frequency relative to another parameter, for example, power supply level. The terms “substantially,”“close,”“approximately,”“near,” and“about,” generally refer to being within +/- 10% of a target value.
[0062] Unless otherwise specified the use of the ordinal adjectives“first,”“second,” and“third,” etc., to describe a common object, merely indicate that different instances of like objects are being referred to, and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner.
[0063] For the purposes of the present disclosure, phrases“A and/or B” and“A or B” mean (A), (B), or (A and B). For the purposes of the present disclosure, the phrase“A, B, and/or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C).
[0064] The terms“left,”“right,”“front,”“back,”“top,”“bottom,”“over,”“under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions.
[0065] For the purposes of present disclosure, the terms“spin” and“magnetic moment” are used equivalently. More rigorously, the direction of the spin is opposite to that of the magnetic moment, and the charge of the particle is negative (such as in the case of electron).
[0066] It is pointed out that those elements of the figures having the same reference numbers (or names) as the elements of any other figure can operate or function in any manner similar to that described, but are not limited to such.
[0067] Fig. 1A illustrates a magnetization hysteresis plot 100 for ferromagnet (FM)
101. The plot shows magnetization response to an applied magnetic field for ferromagnet 101. The x-axis of plot 100 is magnetic field Ή’ while the y-axis is magnetization‘m’. For FM 101, the relationship between Ή’ and‘m’ is not linear and results in a hysteresis loop as shown by curves 102 and 103. The maximum and minimum magnetic field regions of the hysteresis loop correspond to saturated magnetization configurations 104 and 106, respectively. In saturated magnetization configurations 104 and 106, FM 101 has stable magnetizations. In the zero magnetic field region 105 of the hysteresis loop, FM 101 does not have a definite value of magnetization, but rather depends on the history of applied magnetic fields. For example, the magnetization of FM 101 in configuration 105 can be either in the +x direction or the -x direction for an in-plane FM. As such, changing or switching the state of FM 101 from one magnetization direction (e.g., configuration 104) to another magnetization direction (e.g., configuration 106) is time consuming resulting in slower nanomagnets response time. It is associated with the intrinsic energy of switching proportional to the area in the graph contained between curves 102 and 103.
[0068] Fig. IB illustrates magnetization plot 120 for paramagnet 121. Plot 120 shows the magnetization response to an applied magnetic field for paramagnet 121. The x-axis of plot 120 is magnetic field Ή’ while the y-axis is magnetization‘m’. A paramagnet, as opposed to a ferromagnet, exhibits magnetization when a magnetic field is applied to it. Paramagnets generally have magnetic permeability greater or equal to one and hence are attracted to magnetic fields. Compared to plot 100, the magnetic plot 120 of Fig. IB does not exhibit hysteresis which allows for faster switching speeds and smaller switching energies between the two saturated magnetization configurations 124 and 126 of curve 122. In the middle region 125, paramagnet 121 does not have any magnetization because there is no applied magnetic field (e.g., H=0). The intrinsic energy associated with switching is absent in this case.
[0069] In some embodiments, paramagnet 121 comprises a material which includes one or more of: Platinum(Pt), Palladium (Pd), Tungsten (W), Cerium (Ce), Aluminum (Al), Lithium (Li), Magnesium (Mg), Sodium (Na), CnCh (chromium oxide), CoO (cobalt oxide), Dysprosium (Dy), Dy20 (dysprosium oxide), Erbium (Er), Er203 (Erbium oxide), Europium (Eu), EmCb (Europium oxide), Gadolinium (Gd), Gadolinium oxide (Gd203), FeO and Fe203 (Iron oxide), Neodymium (Nd), Nd203 (Neodymium oxide), K02 (potassium superoxide), praseodymium (Pr), Samarium (Sm), Sm203 (samarium oxide), Terbium (Tb), Tb203 (Terbium oxide), Thulium (Tm), Tm203 (Thulium oxide), or V203 (Vanadium oxide). In some embodiments, paramagnet 121 comprises dopants which include one or more of: Ce,
Cr, Mn, Nb, Mo, Tc, Re, Nd, Gd, Tb, Dy, Ho, Er, Tm, or Yb. In various embodiments, the magnet can be either a FM or a paramagnet.
[0070] Figs. 2A-B illustrate a three-dimensional (3D) view 200 and corresponding top view 220, respectively, of a device (also referred to as device 200) having an out-of-plane magnetic tunnel junction (MTJ) stack coupled to a spin orbit coupling (SOC) interconnect, where the MTJ stack includes a free magnet layer much smaller than a length of the SOC interconnect.
[0071] Here, the stack of layers having magnetic juncti on 221 is coupled to an electrode 222 comprising spin Hall effect (SHE) or SOC material, where the SHE material converts charge current Iw (or write current) to spin polarized current Is. The device of Fig. 2A forms a three-terminal memory cell with SHE induced write mechanism and MTJ based read-out. The device of Fig. 2A comprises magnetic junction 221, SHE Interconnect or electrode 222, and non-magnetic metal(s) 223a/b. In one example, MTJ 221 comprises layers 22la, 22lb, and 22lc. In some embodiments, layers 22la and 22lc are ferromagnetic layers. In some embodiments, layer 22lb is a metal or a tunneling dielectric.
[0072] For example, when the magnetic junction is a spin valve, layer 22lb is metal or a metal oxide (e.g., a non-magnetic metal such as Al and/or its oxide) and when the magnetic junction is a tunneling junction, then layer 22lb is a dielectric (e.g. MgO, AhCh). One or both ends along the horizontal direction of SHE Interconnect 222 is formed of non magnetic metals 223a/b. Additional layers 22ld, 22le, 22lf, and 22lg can also be stacked on top of layer 22lc. In some embodiments, layer 22lg is a non-magnetic metal electrode.
[0073] So as not to obscure the various embodiments, the magnetic junction is described as a magnetic tunneling junction (MTJ). However, the embodiments are also applicable for spin valves. A wide combination of materials can be used for material stacking of magnetic j unction 221. For example, the stack of layers 22la, 22lb, 22lc, 22ld, 22le, 22lf, and 22lg are formed of materials which include: CoxFeyBz, MgO, CoxFeyBz, Ru, CoxFeyBz, IrMn, and Ru, respectively, where‘x,’‘y,’ and‘z’ are fractions of elements in the alloys. Other materials may also be used to form MTJ 221. MTJ 221 stack comprises free magnetic layer 22la, MgO tunneling oxide 22lb, a fixed magnetic layer 22lc/d/e which is a combination of CoFe, Ru, and CoFe layers, respectively, referred to as Synthetic Anti- Ferromagnet (SAF), and an Anti-Ferromagnet (AFM) layer 22lf. The SAF layer has the property that the magnetizations in the two CoFe layers are opposite, and allows for cancelling the dipole fields around the free magnetic layer such that a stray dipole field will not control the free magnetic layer.
[0074] In some embodiments, the free and fixed magnetic layers (22la and 22lc, respectively) are formed of CFGG (i.e., Cobalt (Co), Iron (Fe), Germanium (Ge), or Gallium (Ga) or a combination of them). In some embodiments, FM 22la/c are formed from Heusler alloys. Heusler alloys are ferromagnetic metal alloys based on a Heusler phase. Heusler phases are intermetallic with certain composition and face-centered cubic crystal structure. The ferromagnetic property of the Heusler alloys are a result of a double-exchange mechanism between neighboring magnetic ions. In some embodiments, the Heusler alloy includes one of: Cu2MnAl, Cu2MnIn, Cu2MnSn, NfiMnAl, NfiMnln, NfiMnSn, NfiMnSb, Ni2MnGa Co2MnAl, Co2MnSi, Co2MnGa, Co2MnGe, Pd2MnAl, Pd2MnIn, Pd2MnSn, Pd2MnSb, Co2FeSi, Co2FeAl, Fe2VAl, Mn2VGa, Co2FeGe, MnGa, or MnGaRu.
[0075] In some embodiments, fixed magnet layer 22 lc is a magnet with perpendicular magnetic anisotropy (PMA). For example, fixed magnet structure 22 lc has a magnetization pointing along the z-direction and is perpendicular to the x-y plane of the device 200. In some embodiments, the magnet with PMA comprises a stack of materials, wherein the materials for the stack are selected from a group consisting of: Co and Pt; Co and Pd; Co and Ni; MgO, CoFeB, Ta, CoFeB, and MgO; MgO, CoFeB, W, CoFeB, and MgO; MgO, CoFeB, V, CoFeB, and MgO; MgO, CoFeB, Mo, CoFeB, and MgO; MnxGay; Materials with Llo symmetry; and materials with tetragonal crystal structure. In some embodiments, the magnet with PMA is formed of a single layer of one or more materials. In some embodiments, the single layer is formed of MnGa.
[0076] Llo is a crystallographic derivative structure of an FCC (face centered cubic lattice) structure and has two of the faces occupied by one type of atom and the comer and the other face occupied with the second type of atom. When phases with the Llo structure are ferromagnetic the magnetization vector usually is along the [0 0 1] axis of the crystal.
Examples of materials with Llo symmetry include CoPt and FePt. Examples of materials with tetragonal crystal structure and magnetic moment are Heusler alloys such as CoFeAl, MnGe, MnGeGa, and MnGa. [0077] SHE Interconnect 222 (or the write electrode) includes 3D materials such as one or more of b-Tantalum (b-Ta), BiSb, Ta, b-Tungsten (b-W), W, Pt, Copper (Cu) doped with elements such as Iridium, Bismuth and any of the elements of 3d, 4d, 5d and 4f, 5f periodic groups in the Periodic Table which may exhibit high spin orbit coupling. In some embodiments, SHE interconnect 122 comprises a spin orbit 2D material which includes one or more of: graphene, BiSe2, B1S2, BiSexTe2-x, BiSb.TiS. WS2, M0S2, TiSe2, \VSe2. MoSe2, B2S3, Sb2S3, T¾S, Re2.S7, LaCPS2, LaOAsS2, ScOBiS2, GaOBiS2, AIOB1S2, LaOSbS2, BiOBiS2, YOB1S2, InOBiS2, LaOBiSe2, TiOBiS2, CeOBiS2, PrOBiS2, NdOBiS2, LaOBiS2, or SrFBiS2. In some embodiments, the SHE interconnect 222 comprises spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material. In some embodiments, the SHE interconnect 222 comprises a spin orbit material which includes materials that exhibit Rashba-Bychkov effect. In some
embodiments, material which includes materials that exhibit Rashba-Bychkov effect comprises materials ROCh2, where‘R’ includes one or more of: La, Ce, Pr, Nd, Sr, Sc, Ga, Al, or In, and where“Ch” is a chalcogenide which includes one or more of: S, Se, or Te.
[0078] In some embodiments, SHE Interconnect 222 transitions into high
conductivity non-magnetic metal(s) 223a/b to reduce the resistance of SHE Interconnect 222. The non-magnetic metal(s) 223a/b include one or more of: Cu, Co, a-Ta, Al, CuSi, or NiSi.
[0079] In one case, the magnetization direction of fixed magnetic layer 22 lc is perpendicular relative to the magnetization direction of free magnetic layer 22la (e.g., magnetization directions of the free and fixed magnetic layers are not parallel, rather they are orthogonal). For example, the magnetization direction of free magnetic layer 221 a is along the x-y plane of device 200 while the magnetization direction of fixed magnetic layer 22 lc is perpendicular to the x-y plane of device 200. In another case, magnetization direction of fixed magnetic layer 22 la is along the x-y plane of device 200 while the magnetization direction of free magnetic layer 221 c is perpendicular to the x-y plane of device 200.
[0080] The thickness of a ferromagnetic layer (e.g., fixed or free magnetic layer) may determine its equilibrium magnetization direction. For example, when the thickness of the ferromagnetic layer 22la/c is above a certain threshold (depending on the material of the magnet, e.g. approximately 1.5 nm for CoFe), then the ferromagnetic layer exhibits magnetization direction which is in-plane. Likewise, when the thickness of the ferromagnetic layer 22la/c is below a certain threshold (depending on the material of the magnet), then the ferromagnetic layer 22la/c exhibits magnetization direction which is perpendicular to the plane of the magnetic layer. [0081] Other factors may also determine the direction of magnetization. For example, factors such as surface anisotropy (depending on the adjacent layers or a multi-layer composition of the ferromagnetic layer) and/or crystalline anisotropy (depending on stress and the crystal lattice structure modification such as FCC (face centered cubic lattice), BCC (body centered cubic lattice), or Llo-type of crystals, where Llo is a type of crystal class which exhibits perpendicular magnetizations), can also determine the direction of magnetization.
[0082] In this example, the applied current Iw is converted into spin current by SHE
Interconnect 222 (also referred to as the spin orbit coupling interconnect). This spin current switches the direction of magnetization of the free layer and thus changes the resistance of MTJ 221. However, to read out the state of MTJ 221, a sensing mechanism is needed to sense the resistance change.
[0083] The magnetic cell is written by applying a charge current via SHE
Interconnect 222. The direction of the magnetic writing in free magnet layer 221 a is decided by the direction of the applied charge current. Positive currents (e.g., currents flowing in the +y direction) produce a spin injection current with transport direction (along the +z direction) and spins pointing to the +x direction. The injected spin current in turn produces spin torque to align the free magnet 22 la (coupled to the SHE layer 222 of SHE material) in the +x direction. Negative currents (e.g., currents flowing in the -y direction) produce a spin injection current with transport direction (along the +z direction) and spins pointing to the -x direction. The injected spin current in turn produces spin torque to align the free magnet 22 la (coupled to the SHE material of layer 222) in the -x direction. In some embodiments, in materials with the opposite sign of the SHE/SOC effect, the directions of spin polarization and thus of the free layer magnetization alignment are reversed compared to the above.
[0084] Fig. 3 illustrates a cross-section 300 of the SOC interconnect with electrons having their spins polarized in-plane and deflected up and down resulting from a flow of charge current. In this example, positive charge current represented by Jc produces spin-front (e.g., in the +x direction) polarized current 301 and spin-back (e.g., in the -x direction) polarized current 302. The injected spin current ls generated by a charge current Ic in the write electrode 222 is given by:
Figure imgf000016_0001
where, the vector of spin current Is = If— /j, points in the direction of transferred magnetic moment and has the magnitude of the difference of currents with spin along and opposite to the spin polarization direction, z is the unit vector perpendicular to the interface, PSHE is the spin Hall injection efficiency which is the ratio of magnitude of transverse spin current to lateral charge current, w is the width of the magnet, t is the thickness of the SHE
Interconnect (or write electrode) 222, Sf is the spin flip length in SHE Interconnect 222, Q5HE is the spin Hall angle for SHE Interconnect 222 to free ferromagnetic layer interface. The injected spin angular momentum responsible for the spin torque given by:
S = h Is/2e . . . (2)
[0085] The generated spin up and down currents 301/302 (e.g ., /s) are described as a vector cross-product given by:
Figure imgf000017_0001
[0086] This spin to charge conversion is based on Tunnel Magneto Resistance (TMR) which is highly limited in the signal strength generated. The TMR based spin to charge conversion has low efficiency (e.g., less than one).
[0087] Since the spin polarization direction for the SOC materials of Fig. 2A are in plane, a perpendicularly magnetized free magnet layer coupled to SOC interconnect 222 can be switched inefficiently and in the presence of a significant external magnetic field. This means forming devices (e.g., logic and memory) with perpendicular magnetic anisotropy (PMA) are generally a challenge with SOC interconnect 222. Here, perpendicularly magnetized free magnet refers to a magnet having magnetization which is perpendicular to the plane of the magnet as opposed to in-plane magnet that has magnetization in a direction along the plane of the magnet.
[0088] Fig. 4A illustrates a plot 420 showing write energy-delay conditions for one transistor and one MTJ with spin Hall effect (SHE) material compared to traditional MTJs.
[0089] Fig. 4B illustrates plot 430 showing write energy-delay conditions for one transistor and one magnetic tunnel junction (MTJ) with spin Hall effect (SHE) material compared to traditional MTJs. Here, x-axis is energy per write operation in femto-Joules (fJ) while the y-axis is delay in nano-seconds (ns).
[0090] Here, the energy-delay trajectory of SHE and MTJ devices are compared for in-plane magnet switching as the applied write voltage is varied. The energy-delay relationship (for in-plane switching) can be written as:
Figure imgf000017_0002
where Rwrite is the write resistance of the device (resistance of SHE electrode or resistance of MTJ-P or MTJ-AP, where MTJ-P is a MTJ with parallel magnetizations while MTJ-AP is an MTJ with anti-parallel magnetizations, m0 is vacuum permeability, e is the electron charge. The equation shows that the energy at a given delay is directly proportional to the square of the Gilbert damping a. Here the characteristic time, t0 =
Figure imgf000018_0001
/ j v aries as the spin polarization varies for various SHE metal electrodes (e.g., 423, 424, 425). Plot 420 shows five curves 421, 422, 423, 424, and 425. Curves 421 and 422 show write energy-delay conditions using traditional MTJ devices without SHE material.
[0091] For example, curve 421 shows the write energy-delay condition caused by switching a magnet from anti-parallel (AP) to parallel (P) state, while curve 422 shows the write energy-delay condition caused by switching a magnet from P to AP state. Curves 422, 423, and 424 show write energy-delay conditions of an MTJ with SHE material. Clearly, write energy-delay conditions of an MTJ with SHE material is much lower than the write energy-delay conditions of an MTJ without SHE material. While the write energy-delay of an MTJ with SHE material improves over a traditional MTJ without SHE material, further improvement in write energy-delay is desired.
[0092] Fig. 4B illustrates plot 430 comparing reliable write times for spin Hall
MRAM and spin torque MRAM. There are three cases considered in plot 430. Waveform 431 is the write time for in-plane MTJ, waveform 432 is the write time for PMA MTJ, and waveform 433 is the write time for spin Hall MTJ. The cases considered here assume a 30 X 60 nm magnet with 40 kT energy barrier and 3.5 nm SHE electrode thicknesses. The energy- delay trajectories of the devices are obtained assuming a voltage sweep from 0 V to 0.7 V in accordance to voltage restrictions of scaled CMOS. The energy-delay trajectory of the SHE- MTJ devices exhibits broadly two operating regions A) Region 1 where the energy-delay
M Ve /
product is approximately constant (zd < s // ¾ and Region 2 where the energy is
Figure imgf000018_0002
M Ve /
proportional to the delay tά > s j j p The two regions are separated by energy
Figure imgf000018_0003
minima at where minimum switching energy is obtained for the spin
Figure imgf000018_0004
torque devices.
[0093] The energy-delay trajectory of the STT-MTJ (spin transfer torque MTJ) devices is limited with a minimum delay of 1 ns for in-plane devices at 0.7 V maximum applied voltage, the switching energy for P-AP and AP-P are in the range of 1 pJ/write. In contrast, the energy-delay trajectory of SHE-MTJ (in-plane anisotropy) devices can enable switching times as low as 20 ps (b-W with 0.7 V, 20 fj/bit) or switching energy as small as 2 fj (b-W with 0.1 V, 1.5 ns switching time).
[0094] Figs. 5A-B illustrate a 3D view 500 and corresponding cross-section view
520, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, and a via having an in-plane magnet adjacent to the SOC interconnect, according to some embodiments of the disclosure. The oscillator of Fig. 5A is similar to the device of Fig. 2A except that the free magnet 22 la of Fig. 2A is replaced with a structure comprising a stack of layers or films. The magnetic junction is illustrated by reference sign 521 where the layers under layer 22lb (e.g., dielectric or metal/metal-oxide) together form the structure comprising the free magnet of the junction.
[0095] In some embodiments, the structure replacing free magnet 22 la comprises at least two free magnets 52laa and 52lac with a coupling layer 52lab between them, where one of the free magnet couples to (or is adjacent to) the SOC electrode 222 while the other free magnet of the structure couples to or is adjacent to a dielectric (e.g., when the magnetic junction is an MTJ) or a metal or its oxide (e.g., when the magnetic junction is a spin valve). In some embodiments, the structure comprises a first free magnet 52laa having perpendicular magnetization that can point substantially along the + z-axis or - z-axis according to an external field (e.g., spin torque, spin coupling, electric field); a coupling layer 52lab; and a second free magnet 52 lac having perpendicular magnetization that can point substantially along the + z-axis or - z-axis. In various embodiments, the second free magnet 52lac is adjacent to layer 22lb (e.g., dielectric or metal/metal-oxide).
[0096] In some embodiments, the oscillator of Fig. 5A includes an in-plane fixed magnet 524 adjacent to one of the surfaces of the SOC interconnect 222 such that the magnetic junction 521 is formed on the other surface opposite to the surface of the SOC interconnect 222. In some embodiments, the in-plane fixed magnet 524 is thick or long enough in dimensions that results in a stable in-plane magnet that applies an effective in plane field on the perpendicular free magnets 52laa and/or 52 lac for faster switching of free magnets 52laa and/or 52lac. The effective in-plane field can be applied via exchange bias interaction or dipole coupling from the in-plane free magnet 524. As such, an oscillating signal is generated.
[0097] While various embodiments here illustrate the use of the multi-layer free magnet structure being adjacent to a spin Hall effect write electrode 222, the embodiments are applicable to a regular spin transfer torque (SOT) electrode (not shown) which can replace spin Hall effect write electrode 222. [0098] In some embodiments, the coupling layer 521 ab includes one or more of: Ru,
Os, Hs, Fe, or other transition metals from the platinum group of the periodic table. In some embodiments, magnets 52laa, 52 lac, and 524 comprise CFGG. In some embodiments, magnets 52laa, 52lac, and 524 are formed from Heusler alloys. In some embodiments, the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V. In some embodiments, the Heusler alloy includes one of: Cu2MnAl, Cu2MnIn, Cu2MnSn, Ni2MnAl, Ni2MnIn, Ni2MnSn, Ni2MnSb, Ni2MnGa Co2MnAl, Co2MnSi,
Co2MnGa, Co2MnGe, Pd2MnAl, Pd2MnIn, Pd2MnSn, Pd2MnSb, Co2FeSi, Co2FeAl, Fe2VAl, Mn2VGa, Co2FeGe, MnGa, or MnGaRu.
[0099] In some embodiments, magnets 52laa and 52 lac with PMA comprises a stack of materials, wherein the materials for the stack are selected from a group comprising: Co and Pt; Co and Pd; Co and Ni; MgO, CoFeB, Ta, CoFeB, and MgO; MgO, CoFeB, W, CoFeB, and MgO; MgO, CoFeB, V, CoFeB, and MgO; MgO, CoFeB, Mo, CoFeB, and MgO;
MnxGay; Materials with Llo symmetry; or materials with tetragonal crystal structure. In some embodiments, the magnet with PMA is formed of a single layer of one or more materials. In some embodiments, the single layer comprises Mn and Ga (e.g., MnGa).
[00100] While the embodiments of Figs. 5A-B are illustrated with reference to magnets having PMA magnetizations, the embodiments are also applicable to magnets having in-plane magnetizations (not shown). In one such embodiment, the free magnets 52laa and 52lac, and fixed magnet 22lc are in-plane magnets with in-plane magnetizations, while the fixed magnet 524 has perpendicular fixed magnetization to provide an effective out-of-plane field to the in-plane free magnets 521 aa and/or 521 ac. In various embodiments, the in-plane fixed magnet 524 is formed in a via, also referred to as a magnetic via. For example, a hole is first formed and then filled with materials for making an in-plane fixed magnet.
[00101] In some embodiments, the STO operates via a transverse exchange bias from a bottom electrode 222 (e.g., a spin orbit torque electrode or a spin orbit coupling electrode).
In some embodiments, the STO operates via spin injection from a magnetic junction 521 (e.g., spin valve or magnetic tunneling junction (MTJ)) to produce magnetic oscillators in the free magnet layer 52laa/ac of the magnetic junction 531.
[00102] In some embodiments, spin Hall current (e.g., IsH-controi) interacts with the free magnet layer (or structure) 52laa/ac to produce self-sustained oscillations/excitations. In some embodiments, a second tunneling excitation current (Isense-controi) interacts with an in plane or perpendicularly polarized free magnet layer 52laa/ac to produce or ensure self- sustained oscillations. In some embodiments, the path through the magnetic junction 531 provides a sensing path generating an AC current at the oscillation frequency. In some embodiments, the path through the spin Hall electrode 222 provides a path to connect spin Hall oscillators for coupling the state of the oscillators.
[00103] Figs. 6A-B illustrate a 3D view 600 and corresponding cross-section view 620, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, and a via comprising an in-plane magnet and an anti- ferromagnet (AFM) one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure. The oscillator of Fig. 6A is similar to the oscillator of Fig. 5A, but for addition of AFM 625 in the magnetic via. In some embodiments, the in-plane fixed magnet 524 of the magnetic via is coupled to or is adjacent to an in-plane anti- ferromagnet (AFM) or synthetic AFM (SAF) 625 also formed in the magnetic via. The order of the AFM 625 and in-plane fixed magnet 524 can be switched. For example, in some embodiments, AFM 625 is adjacent to SOC interconnect 222 while the in-plane fixed magnet 524 is below AFM 625 and not in direct contact with SOC interconnect 625.
[00104] In some embodiments, AFM or SAF 625 comprises a material which includes one of: Ir, Pt, Mn, Pd, or Fe. In some embodiments, AFM or SAF 625 is a quasi-two- dimensional triangular AFM including Ni(i-X)MxGa2S4, where‘M’ includes one of: Mn, Fe,
Co or Zn. In some embodiments, AFM or SAF 625 comprises a pair of fixed magnets 625a and 625c with in-plane magnetizations, and a coupling layer 625b between the fixed magnets 625a and 625c. In some embodiments, the materials for the fixed magnets 625a/c can be according to any of the materials for magnets discussed herein. In some embodiments, the material for coupling layer 625b can be the same material (or selected from the same group of materials) as that of coupling layer 52lab. Technical effect wise, the oscillator of Fig. 6A performs similarly to the oscillator of Fig. 5A, and provides an oscillating signal.
[00105] Figs. 7A-B illustrate a 3D view 700 and corresponding cross-section view 720, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where an AFM is embedded in the SOC interconnect, and a via comprising an in-plane magnet which is adjacent to the AFM, according to some embodiments of the disclosure. The oscillator of Fig. 7A is similar to the oscillator of Fig.
6A except that the AFM 625 is removed and incorporated outside the magnetic via as AFM 722 adjacent to SOC interconnect 222. In some embodiments, AFM 722 can behave as an etch stop layer when fabricating SOC interconnect 222. As such, one or more additional processes for forming an etch stop layer is/are removed. In various embodiments, AFM 722 assists with keeping the magnetization of magnet 525 stable with in-plane magnetization. In some embodiments, AFM 722 also comprises a pair of fixed magnets (not shown) with in plane magnetizations, and a coupling layer between the fixed magnets like AFM 625.
Technical effect wise, the oscillator of Fig. 7A performs similarly to the oscillators of Figs. 5-6, and provides an oscillating signal.
[00106] Figs. 8A-B illustrate a 3D view 800 and corresponding cross-section view 820, respectively, of an oscillator having a magnetic junction with magnets having perpendicular magnetizations, where an AFM electrode replaces the SOC interconnect, and where the oscillator further comprises a via including an in-plane magnet which is adjacent to the AFM, according to some embodiments of the disclosure. The device of Fig. 8A is similar to the device of Fig. 5A except that the SOC interconnect 222 is replaced with AFM interconnect 722. Technical effect wise, the oscillator of Fig. 8A performs similarly to the oscillators of Figs. 5-7, and provides an oscillating signal.
[00107] Fig. 9 illustrates a cross-section 900 of a cascaded SOC oscillators with charge based coupling between the SOC interconnects, which produces a charge based spin current excitation, in accordance with some embodiments. In some embodiments, two (or more)
SOC oscillators 901 and 902 are cascaded such that the SOC interconnects of SOC oscillator 901 and SOC oscillator 902 are coupled together. In this example, the SOC oscillators are based on the oscillator of Fig. 5B. However, any of the oscillators from Figs. 5-9, and Fig.
22 can be used for either of oscillators 901 or 902.
[00108] Oscillators can be connected together in multiple ways. For example, the spin orbit electrode 222 of one MTJ can be connected to another MTJ. In this example, the output of one oscillator read across the MTJ can also be fed to the other MTJ by connecting layer 22lg via a common electrode. As such, the oscillators work in parallel configuration. Other form of coupling replay on spacing the oscillators close to one another allowing for their magnetic fields to be coupled by proximity effect, in accordance with some embodiments.
[00109] Fig. 10 illustrates a scheme 1000 of an oscillatory Cellular Neural Network (CNN) that uses the SOC based oscillators, according to some embodiments. CNN are a parallel computing networks in which communication is allowed between neighboring units. CNN processors are a system of nonlinear processing units. These nonlinear processing units may be a finite, fixed-number, fixed-location, fixed-topology, locally interconnected, multiple-input, and/or single-output. CNN processors can be used for image processing and pattern recognition. One such scheme used for image processing is a rectangular array of SOT or SOC oscillators as shown in Fig. 10. The SOT or SOC oscillators (OSCs) are coupled together via inductors L0. In this example, an NxN array of OSCs lOOloo through IOOINN are shown, where each SOT or SOC OSC is a cell or neuron, and where‘N’ is an integer.
[00110] Figs. 11A-B illustrate a three terminal (3T) high input impedance STO or SOC oscillator 1100 with built-in Mixer, according to some embodiments of the disclosure.
In some embodiments, apparatus 1100 comprises STO 1101 (e.g., any one of SOT or SOC oscillators of Figs. 5-8 and Fig. 22), Bias-T (or Bias-Tee) network 1102, Isolator 1103, and first, second, and third non-magnetic conductors H04a, H04b, and H04c, respectively.
[00111] In some embodiments, STO 1101 includes a magnetic junction having free and fixed magnetic layers such that one of the magnetic layers is an in-plane magnet and another is a perpendicular magnet. In some embodiments, the free and fixed magnetic layers are separated by a metal. In one such embodiment, the magnetic junction is a spin valve. In some embodiments, the free and fixed magnetic layers are separated by a dielectric (e.g., MgO, AI2O3). In one such embodiment, the magnetic junction is a magnetic tunneling junction (MTJ).
[00112] In some embodiments, STO 1101 includes a spin orbit coupling (SOC) layer (e.g., interconnect 222) coupled to the free magnet 52laa of the magnetic junction (e.g., 521) In some embodiments, the SOC layer is biased by a SOC DC bias. In some embodiments, this DC bias defines in-part the center frequency of oscillation of STO 1101. In some embodiments, the SOC layer is coupled to first and second non-magnetic conductors 1 l04a/b on either ends of the SOC layer, respectively. In some embodiments, the fixed magnet of STO 1101 is coupled directly or indirectly to a metal electrode which in turn is coupled to the third non-magnetic conductor 1 l04c. In some embodiments, an input RF signal (RFIN) is provided to the first non-magnetic conductor 1 l04a. In one such embodiment, the input impedance ZIN of apparatus 1100 is high because the impedance looking into apparatus 1100 sees non-magnetic conductors l04a/b.
[00113] In some embodiments, Bias-T 1102 biases STO 1101 with a DC bias. In some embodiments, this DC bias defines in-part the center frequency of oscillation of STO 1101.
In some embodiments, Bias-T 1102 is a three port network (often arranged in a T shape) which is used for setting the DC bias point of STO 1101 without disturbing other components. In some embodiments, Bias-T 1102 is a diplexer. Conceptually, Bias-T 1102 can be viewed as an ideal capacitor that allows AC (alternating current) through but blocks the DC bias and an ideal inductor that blocks AC but allows DC (direct current). [00114] In some embodiments, the low frequency port of Bias-T 1102 is used to set the bias. Here, the low frequency port receives the DC bias and control. In some embodiments, a first high frequency port of Bias-T 1102 passes the RF signals but blocks the biasing levels. For example, low frequency IF signal, which is down modulated from the RF input at the Zin port by the STO, is received at the output of Isolator 1103 (e.g., IF OUT). In some
embodiments, the first high frequency port of Bias-T 1102 is coupled to Isolator 1103. In some embodiments, a second high frequency port of Bias-T 1102 passes both the RF signal and the DC bias. Here, the second high frequency port of Bias-T 1102 is coupled to third non-magnetic conductor 1104a.
[00115] In some embodiments, Isolator 1103 isolates Bias-T 1102 from other components. In some embodiments, Isolator 1103 is a non-reciprocal device, with a non- symmetric scattering matrix. In some embodiments, Isolator 1103 suppresses backward reflection of RF signal from the detection circuitry (i.e., from STO 1101).
[00116] In some embodiment, an intermediate frequency output (IFOUT) is provided across Isolator 1103 and second non-magnetic conductor 1 l04b. This IFOUT is the down converted RFIN signal. In some embodiments, the output impedance ZOUT across Isolator 1103 and second non-magnetic conductor 1 l04b is high impedance. In some embodiments, another Isolator (not shown) is provided at the input and coupled to non-magnetic conductor 1104a. As such, RFIN is provided uni-directi onally to the non-magnetic conductor 1104a. In some embodiments, Isolator 1103 is optional and can be removed.
[00117] In some embodiments, STO 1101 receives RFIN and down converts it to IFOUT using the oscillation behavior of STO 1101 and its built-in mixer function. In some embodiments, the oscillation behavior of STO 1101 is achieved from the metastability of the perpendicular magnet and the in-plane magnet. In some embodiments, when the input RF current of the RF signal is provided to the SOC layer of STO 1101, STO 1101 begins to oscillate and mixes the RF signal to a lower frequency (e.g., down converts it).
[00118] While some embodiments describe the apparatus for amplitude modulation, the same concept can be extrapolated for FM (frequency modulation) and PM (phase modulation). For FM, a filter is used with a roll-off. In some embodiments, this filter is placed after Isolator 1103 as illustrated by filters 1602 in Fig. 16. Fig. 11B is similar to Fig. 11A but for showing the oscillator 1101 which can be any of the devices of Figs. 5-9 and Fig. 22
[00119] Fig. 12A illustrates a plot 1200 showing a single-sided amplitude spectrum of an input RF signal which is input to the 3T STO with built-in Mixer, according to some embodiments of the disclosure. Here, x-axis is frequency (GHz) and y-axis is magnitude of the power spectral density of the measured current from MTJ.
[00120] Fig. 12B illustrates a plot 1220 showing magnetization oscillation produced by the 3T STO with built-in Mixer, according to some embodiments of the disclosure. In some embodiments, the oscillation is produced by the metastability caused by the
magnetization direction 1221 of the magnet of STO 1101 with perpendicular anisotropy relative to the magnetization direction 1222 of the magnet of STO 1101 with in-plane anisotropy. Here, plot 1220 shows the magnetic dynamics of STO 1101 with continuous oscillations centered at 7.5 GHz.
[00121] Fig. 12C illustrates a plot 1230 showing a single-sided amplitude spectrum of the output of the 3T STO with built-in Mixer, according to some embodiments of the disclosure. Plot 1230 shows that IFouThas a frequency of 1.5 GHz which is produced by down converting of RFIN from 9 GHz via STO 1101, in accordance with some embodiments. In some embodiments, the frequency of the down converted signal can be adjusted by adjusting the DC bias and control to Bias-T 1102 (which in turn biases STO 1101) and/or the DC bias of SOC bias. In some embodiments, the down converted signal is detected and processed by a digital signal processing logic (not shown).
[00122] Fig. 13A-B illustrate a 3T low input impedance STO or SOC oscillator 1300 with built-in Mixer, according to some embodiments of the disclosure. Compared to apparatus 1100, here STO 1101 is oriented such that ZIN is low compared to ZIN of apparatus 1100. In some embodiments, when RFIN is received by apparatus 1300 such that RFIN sees the SOC layer of STO 1101 instead of first and third non-magnetic conductors 1 l04a/c (as in apparatus 1100), RFIN sees lower impedance because the SOC layer 222 has lower impedance than first and third non-magnetic conductors H04a/c. As such, apparatus 1300 can be used for RF applications that desire lower input impedance while apparatus 1100 can be used for RF applications that desire higher input impedance. Fig. 13B is similar to Fig. 13A but for showing the oscillator 1101 which can be any of the devices of Figs. 5-9 and Fig. 22
[00123] Fig. 14 illustrates an RF detection apparatus 1400 for Magnetic Resonance Imaging (MRI) having the 3T STO with built-in Mixer, according to some embodiments of the disclosure, according to some embodiments of the disclosure.
[00124] In some embodiments, apparatus 1400 comprises an RF Receiver (Rx) 1401, Balun 1402, Low Noise Amplifier 1403, STO apparatus 1404 (e.g., apparatus 1100, 1120, 1300, 1320), and Digital Signal Processing logic 1405. [00125] In some embodiments, RF Rx 1401 is an Rx coil or antenna array with a preferred quality factor Q (e.g., in the range of 1 to 100) tuned to the incoming
RF/electromagnetic radiation. One such embodiment of RF Rx 1401 is illustrated as an RF receiver coil with controlled detuning of the RF detection apparatus 100, in accordance with some embodiments of the disclosure.
[00126] In some embodiments, RF receiver coil 1401 comprises a loop having inductor L and capacitor C pairs 1421. The loop defines an RF signal collection area 1422, in accordance with some embodiments. In this example, four pairs of L and C are shown. In each pair of L and C, L and C are coupled together in parallel. In some embodiments, a detuning circuit is integrated in the loop. In some embodiments, the detuning circuit comprises of active and/or passive devices. In some embodiments, the detuning circuit includes diode 1423 with an anode terminal coupled to one L and C pair and a cathode coupled to another L and C pair.
[00127] In some embodiments, diode 1423 is controlled via a control signal. In some embodiments, the control signal provides RF protection to the sensitive receive electronics.
In some embodiments, the control signal detunes the coil by adding resistance. For example, control signal adds resistive loss to detune the high Q of the oscillator. In the case of MRI, the chamber of MRI coils is pulsed with electromagnetic pulses (e.g., killo Watt pulses). In some embodiments, the anode and cathode of diode 1423 are also coupled to inductors which receive the input RF signal. In some embodiments, the detuning circuit controls the center frequency and/or the quality factor of the RF circuit. In some embodiments, the detuning circuit can be a MEMS (micro-electrical-mechanical-system) switch to enable high contrast switching with EMI (electromagnetic interference) resistance.
[00128] In some embodiments, Balun 1402 couples to RF Rx 1401 and to LNA 1403. One embodiment of Balun 1402 is illustrated as a common-mode choke that suppresses common mode noise due to DC signal or due to electromagnetic induction. For example, if RF Rx 1401 picks up unwanted charge, that unwanted charge is choked by Balun 1402. In some embodiments, Balun 1402 is implemented using mutual inductors Ll and L2 and/or solenoids.
[00129] In some embodiments, LNA 1403 is coupled to Balun 1402 and STO apparatus 1404. In some embodiments, LNA 1403 amplifies the very weak signals captured by an antenna or RF Rx 1401 and provided to LNA 1403 via Balun 1402. Essentially, signals that are barely recognizable are amplified by LNA 1403 without adding a lot of noise. LNA 1403 has a low Noise Figure (NF). For example, LNA 1403 has a NF of ldB (decibel) and a high gain (e.g., 20dB).
[00130] In some embodiments, STO apparatus 1404 receives the amplified RF signal from LNA 1403 and down converts it to IF signal with its built-in oscillator and mixer. In some embodiments, the IF signal is provided to DSP 1405. Any known suitable DSP may be used for implementing DSP 1405.
[00131] Fig. 15 illustrates an RF detection apparatus 1500 for a wireless receiver having the 3T STO with built-in Mixer, according to some embodiments of the disclosure. In some embodiments, RF Rx coil 1401 and Balun 1402 are removed and replaced with
Antenna 1501. In some embodiments, Antenna 1501 may comprise one or more directional or omnidirectional antennas, including monopole antennas, dipole antennas, loop antennas, patch antennas, microstrip antennas, coplanar wave antennas, or other types of antennas suitable for transmission of RF signals. In some multiple-input multiple-output (MIMO) embodiments, Antenna(s) 1501 are separated to take advantage of spatial diversity.
[00132] Fig. 16 illustrates an apparatus 1600, with the 3T STO having built-in Mixer, showing parallel sensing using multiple receiver coils at a single frequency, according to some embodiments of the disclosure. In some embodiments, apparatus 1600 comprises a space division multiplexed signal array that includes antennas 1601 I-N, STOS 1 101 I-N, 1 102I- N, Isolators 1103 I-N, and filters 1602I-N. Here, each antenna is coupled to an STO that generates an output RF signal A(t)=sin(coLt)sin(coLt- icokt) of the same frequency co, where co= on.- (Ok, and A(t) is the time domain amplitude, OIL is the Larmor frequency or the center frequency of the receive signal band, and OIL is the frequency division multiplexing (FDM) frequency. For example, antenna 16011 is coupled to STO 11011 which provides an RF output signal to Bias-T 11021.
[00133] In some embodiments, the output of Bias-T 11021 is received by Isolator 11031 and then filtered by filter 1602i. The output of filter 1602i is then processed by a DSP logic. One reason for being able to form a parallel sensing apparatus 1600 is the small size of STO compared to transitional mixers with local oscillating clock sources. As such, many antennas with RF detection circuits (with STOs) can be used in a small form factor to detect and process data in parallel.
[00134] Fig. 17 illustrates an apparatus 1700, with the 3T STO having built-in Mixer, showing parallel sensing with frequency multiplexing, according to some embodiments of the disclosure. Compared to apparatus 1600, here frequency division multiplexing (FDM) is used to reduce the number of wires, in accordance with some embodiments. As such, an even smaller form factor is achievable than apparatus 1600. In some embodiments, each STO operates at a different oscillation frequency. For example, STO 11011 operates at coi, STO 1 lOb operates at C02, and STON operates at CON, where‘N’ is an integer greater than two. As such, the output of all STOs is a summation of RF signals with different frequencies.
[00135] In some embodiments, because each STO is tuned to operate at a different frequency, the same interconnect can be used to collect all RF signals output from the STOs. As such, the number of interconnects are reduced compared to apparatus 1600. In some embodiments, the frequency of each STO may be defined by the nature of the input RF signal. For example, for MRI, the center frequency is 64 MHz to 128 MHz, for cellular and adhoc wireless networks the center frequency is 500 MHz to 3 GHz, and for millimeter wave, the center frequency is 60 GHz. All these ranges are viable with STOs.
[00136] The RF signal’s carrier frequency is the same for each input but the center oscillating frequency of the STOs is different by n x oik. In some embodiments, the IF signal goes to a bandpass filter where the center frequency of the bandpass filter in the IF output after the isolator is n x oik. In some embodiments, the signal is reconstructed in the DSP (this is done to create a higher power receive signal and thus higher S/N ratio). In some embodiments, the STOs l lOh-N are tuned to the operating frequencies coi-Nvia the feedback provided from the DC bias and control to Bias-T 1102.
[00137] In some embodiments, filters are used to detect the respective RF signal. In some embodiments, filters 1702I-N are centered at oik. 2 oik.3 oik. . . Non, where‘N’ is an integer greater than three. For example, filter 1702i is used to detect RF signal having frequency on, where on = on. - on, filter 17022 is used to detect RF signal having frequency 012, where 012 = on. - 2 on, and filter H 02N is used to detect RF signal having frequency CON, where oi3 = on. - Non, where‘N’ is an integer greater than two. In some embodiments, the filters can be present on the device near the STOs or can be in a remote location (i.e., away from the STOs). Any suitable filter can be used for implementing filters 1702I-N.
[00138] Fig. 18 illustrates a sensing array 1800 formed with the apparatus of Fig. 16, according to some embodiments of the disclosure. Sensing array 1800 applies the parallel sensing scheme of apparatus 1600. Here, an MxN array is formed with antennas of RF Rx coils 1801NM and STOs I I OINM tuned to a single frequency co, where‘M’ is the number of columns (e.g., 4) and‘N’ is the number of rows (e.g., 5). In some embodiments, each column of sensing array 1800 results in‘N’ number of wires that carry respective down converted RF (IF) signals for further processing. As such, sensing array 1800 generates MxN wires with MxN down converted IF signals for DSP logic 1405 to process. The size of sensing array 1800 is small enough that it can fit in modem hand-held devices without having varacters and inductors, in accordance with some embodiments.
[00139] Fig. 19 illustrates a sensing array 1900 formed with the apparatus of Fig. 16, according to some embodiments of the disclosure. Sensing array 1900 applies the parallel sensing scheme of apparatus 1800. In some embodiments, RF signal can be collected via‘M’ wires where each column is a frequency multiplexed arrangement of RF receivers.
Compared to sensing array 1800, sensing array 1900 has significantly fewer number of interconnects allowing for further reduction in the form factor of the arrays.
[00140] STO based RF detection described with reference to various embodiments allows for massively parallel RF detection comprising of detecting elements in excess of 1000 detectors. In comparison, the RF detection schemes used in the state of the art MRI is only limited to 24 channels. The STO based RF detection of the various embodiments also improves signal collection times for sensing. Sensing time is approximately proportional to l/(number of channels). The STO based RF detection of the various embodiments has a capability of being turned on the fly as required by the application or electromagnetic environment. For example, by adjusting the DC bias control to Bias-T 1102 and/or by adjusting the DC Bias-To SHE interconnect 222, operating frequency of the STO can be adjusted. Since the mixer and local oscillator functions are integrated in one device, the STO based RF detection of the various embodiments reduces the area of the RF detection scheme.
[00141] Fig. 20A illustrates an equivalent vector spin circuit 2000 for STO RF detector with locally generated oscillator, according to some embodiments of the disclosure. STO 1101 can be modeled using vector spin circuit theory comprising a 4x4 conduction matrix formulation for spin transport coupled with magnetization dynamics, in accordance with some embodiments. Model 2000 can be self-consistently coupled to the nano-magnet dynamics including the thermal stochastic noise effects, in accordance with some
embodiments. The spin torque acting on the free layer in a spin-orbit torque MTJ (e.g., 521) originates from spin torque due to spin injection from the fixed layer, and from spin torque due to the spin orbit torque acting on the free layer.
[00142] The phenomenological equation describing the dynamics of nanomagnets with the magnetic moment unit vector (m) is the modified Landau-Lifshitz-Gilbert-Slonczewski (LLG) equation expressed as:
Figure imgf000029_0001
where g is the electron gyromagnetic ratio; q0is the free space permeability; He^ (T)\s the effective magnetic field due to material, shape, and surface anisotropies, with the thermal noise component and Tslm = (in x in x Is) is the component of vector spin current perpendicular to the magnetization, and Ns is the total number of Bohr magnetons in the magnet. The dynamics of the magnetic junction (e.g., MTJ 521) are solved self-consistently with the spin transport in the equivalent circuit models.
[00143] The equivalent vector spin circuit for the magnetic junction (e.g., MTJ 521) comprises of the equivalent spin conductance of the fixed Ferromagnet (FMfixed) and free Ferromagnet (FMocc) interfaces to form the magnetic junction (e.g., MTJ 521). The vector spin equivalent circuit model for MTJ 521 is in model 2000. In some embodiments, model 2000 comprises of three nodes NO, Nl and N2 to describe MTJ 521. The RF input is applied to nodes 3 to 5 (or the low impedance configuration of Fig. 13. The IF output is collected across nodes 5 and 0, in accordance with some embodiments.
[00144] The magnetization of the top fixed layer and the bottom free layer are described by rhfixmd in^ree. The 4-component conductivity of the FM1 and oxide interface is described by GFMI and the conductivity of the FM2 and the oxide interface is described by GFM2. The conductance matrix describing the spin transport across a FM/Oxide interface can be written as:
Figure imgf000030_0001
where Gn is the interface conductivity (per interface) of the FM/MgO interface, a(V) is the spin polarization across the interface as a function of voltage, and GSL(VC) and GFL(Vc) are Slonczewski and field like torque contributions from the tunneling spin current across the interface. The voltage dependence of spin polarization a(V), GSL(V), and GFL (V) is dependent on the detailed band structure of the electrodes and tunneling materials. The effect of magnetization rotation for a precessing MTJ 521 can be described using the proposed model, where the 4 component conductance evolve as a function of the magnetization of the free magnet.
GFMo(fi = R(m)_1GFM0(x)R(m)
where R(in) is a 4-component transformation to rotate the conductance matrices. [00145] The spin torque from tunneling spin currents acting on the magnet and the effect of spin torque from spin orbit layer are included via a spin injection into the free layer as governed by the physics of spin injection from SHE layer 222 to FM layer. The equivalent spin circuit model includes a current control spin current to model the injection of spin current from SHE 222 to the free magnet layer. Here, the field like component of spin orbit torque is also added via a current controlled effective magnetic field due to spin orbit torque.
[00146] Fig. 20B illustrates a plot 2020 showing tunability of the STO, according to some embodiments of the disclosure. Here x-axis is Voltage (V) and y-axis is Frequency (GHz). A simulation of the tunable spin torque dynamics of the SHE oscillator driven by the spin current response from a vector spin circuit model 2000 is shown by plot 2020. The vector magnetization dynamics of the free layer showing tunability of the local oscillator due to the combined action of anti-damping spin torque and effective field due to spin orbit effects is shown in plot 2020. An input RF signal centered at 10 GHz is shown in Fig. 12A, while the local oscillator dynamics are shown in the inset. The output of the RF detector across nodes 5 and 0 is shown in Fig. 12C. The simulations of Figs. 12A-C assume a 70 kT magnet with dimensions of 20 X 60 nm and with spin orbit metallic electrode of 60 X 60 nm of resistivity 200 pm. cm. In this simulation example, the bulk spin hall ratio is 0.15 and the effective Rashaba field is 8 c 10 6 Oe/(A/cm2) for the transient vector spin simulations.
[00147] Fig. 21A illustrates a cross-section 2100 of an oscillator having a magnetic junction 2121 with magnets having perpendicular magnetizations, where a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[00148] The magnetic junction here is illustrated by reference sign 2121 where the layers under layer 22lb (e.g., dielectric or metal/metal-oxide) together form the structure comprising the free magnet of the junction. The device of Fig. 21A is similar to the device of Fig. 5A except that the free magnets 52laa and 52lae are replaced with composite magnets having multiple layers.
[00149] In some embodiments, the composite stack of multi-layer free magnet 2l2laa includes‘n’ layers of first material and second material. For example, the composite stack comprises layers 2l2laai-n and 2l2labi-n stacked in an alternating manner, where‘n’ has a range of 1 to 10. In some embodiments, the first material includes one of: Co, Ni, Fe, or an Heusler alloy. In some embodiments, the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V. In some embodiments, the Heusler alloy includes one of: Cu2MnAl, Cu2MnIn, Cu2MnSn, NfMnAl, Ni2MnIn, Ni2MnSn, Ni2MnSb, Ni2MnGa Co2MnAl, Co2MnSi, Co2MnGa, Co2MnGe, Pd2MnAl, Pd2MnIn, Pd2MnSn, Pd2MnSb, Co2FeSi, Co2FeAl, Fe2VAl, Mn2VGa, Co2FeGe, MnGa, or MnGaRu. In some embodiments, the first material has a thickness tl in a range of 0.6 nm to 2 nm. In some embodiments, the second material has a thickness t2 in a range of 0.1 nm to 3 nm. While the embodiments here show first material being at the bottom followed by the second material, the order can be reversed without changing the technical effect.
[00150] In some embodiments, composite stack of multi-layer free magnet 2l2lbb includes‘n’ layers of first material and second material. For example, the composite stack comprises layers 2l2laai-n and 2l2labi-n stacked in an alternating manner, where‘n’ has a range of 1 to 10. In some embodiments, the first material includes one of: Co, Ni, Fe, or a Heusler alloy. In some embodiments, the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V. In some embodiments, the Heusler alloy includes one of: Cu2MnAl, Cu2MnIn, Cu2MnSn, Ni2MnAl, Ni2MnIn, Ni2MnSn, Ni2MnSb, Ni2MnGa Co2MnAl, Co2MnSi, Co2MnGa, Co2MnGe, Pd2MnAl, Pd2MnIn, Pd2MnSn, Pd2MnSb, Co2FeSi, Co2FeAl, Fe2VAl, Mn2VGa, Co2FeGe, MnGa, or MnGaRu. In some embodiments, the first material has a thickness tl in a range of 0.6 nm to 2 nm. In some embodiments, the second material has a thickness t2 in a range of 0.1 nm to 3 nm. While the embodiments here show first material being at the bottom followed by the second material, the order can be reversed without changing the technical effect. Here, magnetization for composite magnet 2l2laa is 1201 (e.g., +z or -z directions), magnetization or composite magnet 2l2lbb is 1202 (e.g., +z or -z directions), and magnetization of fixed magnet 22 lc is 2103.
[00151] The embodiments of Figs. 5-9 can be mixed in any order. For example, the in-plane magnet 524 can be replaced with an AFM magnet, free magnet structure with free magnets and coupling layer can be replaced with a single magnet with free magnetization, in plane magnets can be replaced with perpendicular magnets. In some embodiments, the magnets (free and/or fixed) can also be paramagnets.
[00152] Fig. 21B illustrates a cross-section 2130 of a oscillator having a magnetic junction 2131 with magnets having perpendicular magnetizations, where a free magnet structure and a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure.
[00153] In some embodiments, composite stack of multi-layer fixed magnet 2l2lcc includes‘n’ layers of first material and second material. For example, the composite stack comprises layers 2l2laai-n and 2l2labi-n stacked in an alternating manner, where‘n’ has a range of 1 to 10. In some embodiments, the first material includes one of: Co, Ni, Fe, or Heusler alloy. In some embodiments, the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V. In some embodiments, the Heusler alloy includes one of: Cu2MnAl, CmMnln. CmMnSn. NfiMnAl, Ni2MnIn, Ni2MnSn, Ni2MnSb, Ni2MnGa Co2MnAl, Co2MnSi, Co2MnGa, Co2MnGe, Pd2MnAl, Pd2MnIn, Pd2MnSn, Pd2MnSb, Co2FeSi, Co2FeAl, Fe2VAl, Mn2VGa, Co2FeGe, MnGa, or MnGaRu. In some embodiments, the first material has a thickness t3 in a range of 0.6 nm to 2 nm. In some embodiments, the second material has a thickness t4 in a range of 0.1 nm to 3 nm. While the embodiments here show the first material being at the bottom followed by the second material, the order can be reversed without changing the technical effect.
[00154] Fig. 21C illustrates a cross-section 2150 of a oscillator having a magnetic junction 2151 with magnets having perpendicular magnetizations, where a fixed magnet structure and one of the free magnets of a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure. Here, free magnet 2l2lbb of Fig. 21C is replaced with a non-composite free magnet 521 ac. As such, the magnetic junction is labeled as 2151.
[00155] Fig. 21D illustrates a cross-section 2160 of a oscillator having a magnetic junction with magnets having perpendicular magnetizations, where a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure. Here, free magnet 2121 aa of Fig. 21D is replaced with a non-composite free magnet 521 aa. As such, the magnetic junction is labeled as 2161.
[00156] Fig. 21E illustrates a cross-section 2170 of a oscillator having a magnetic junction 2171 with magnets having perpendicular magnetizations, where a fixed magnet structure and one of the free magnets of a free magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in- plane magnet and/or an AFM, one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure. Here, free magnet 82laa of Fig. 21B is replaced with a non-composite free magnet 52laa. As such, the magnetic junction is labeled as 2171.
[00157] Fig. 21F illustrates a cross-section 2180 of a oscillator having a magnetic junction 2181 with magnets having perpendicular magnetizations, where a free magnet structure and a fixed magnet structure of the magnetic junction comprises a stack of magnets with perpendicular magnetizations, and a via comprising an in-plane magnet which is adjacent to an AFM embedded in the SOC interconnect, according to some embodiments of the disclosure. Compared to Fig. 21A here, the AFM 625 is removed from the magnetic via and integrated in the SOC interconnect 222 as layer 722.
[00158] Fig. 22 illustrates a flowchart 2200 of a method for forming an SOT or SOC based oscillator, in accordance with some embodiments. While the following blocks (or process operations) in the flowchart are arranged in a certain order, the order can be changed. In some embodiments, some blocks can be executed in parallel.
[00159] At block 2201, a first magnetic junction is formed. At block 2202, a second magnetic junction is formed. At block 2203, an interconnect is formed adjacent to the first and second magnetic junctions. At block 2204, a first structure is formed adjacent to the interconnect such that the first structure is under the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device. At block 2205, a second structure is formed adjacent to the interconnect such that the second structure is under the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the plane of the device.
[00160] In some embodiments, the method of forming the interconnect comprises forming a first section and a section coupled to the first section via a conducting material. In some embodiments, the magnet of the first structure is adjacent to the first section, and wherein the magnet of the second structure is adjacent to the second section. In some embodiments, the first section or second section comprises an antiferromatic (AFM) material. In some embodiments, the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe. In some embodiments, the AFM material is a quasi-two-dimensional triangular AFM including Nip- x)MxGa2S4, where‘M’ includes one of: Mn, Fe, Co or Zn. In some embodiments, the first section or second section comprises: one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b- W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth or elements of 3d, 4d, 5d and 4f, 5f periodic groups, Ti, S, W, Mo, Se, B, Sb, Re, La, C, P, La, As, Sc, O, Bi, Ga, Al, Y, In, Ce, Pr, Nd, F, Ir, Mn, Pd, or Fe. [00161] In some embodiments, the first section or second section comprises: spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material. In some embodiments, the first section or section comprises: a spin orbit material which includes materials that exhibit Rashba-Bychkov effect. In some embodiments, the first or second magnetic junctions is one of a spin valve or a magnetic tunneling junction (MTJ).
[00162] In some embodiments, the method of forming the first or second magnetic junctions include: forming a stack of structures includes: forming a first structure comprising a magnet with an unfixed perpendicular magnetic anisotropy (PMA), wherein the first structure has an anisotropy axis perpendicular to the plane of the device; forming a second structure comprising one of a dielectric or metal; forming a third structure comprising a magnet with fixed PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations are in-plane magnetizations.
[00163] In some embodiments, the method of forming the first or second magnetic junctions include: forming a stack of structures including: forming a first structure comprising a magnet with an unfixed in-plane magnetic anisotropy, wherein the first structure has an anisotropy axis along the plane of the device; forming a second structure comprising one of a dielectric or metal; forming a third structure comprising a magnet with fixed in-plane magnetic anisotropy, wherein the third structure has an anisotropy axis along the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations have perpendicular magnetic anisotropy (PMA).
[00164] In some embodiments, the method of forming the magnetic junction comprises: forming a fourth structure between the first and second structures, wherein the fourth structure includes one or more of: Ru, Os, Hs, or Fe. In some embodiments, the method of forming the magnetic junction comprises forming a fifth structure between the second and third structures, wherein the fifth structure includes one or more of: Ru, Os, Hs, or Fe. In some embodiments, the method of forming the first structure comprises forming an antiferromagnet (AFM) adjacent to the magnet of the first structure, and wherein the second structure comprises an AFM adjacent to the magnet of the second structure. In some embodiments, the fourth structure is between the interconnect and an eighth structure, wherein the eighth structure includes an antiferromagnet (AFM). In some embodiments, the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
[00165] In some embodiments, the AFM material is a quasi-two-dimensional triangular AFM including Ni(i-X)MxGa2S4, where‘M’ includes one of: Mn, Fe, Co or Zn. In some embodiments, the magnets of the first and/or second structures comprises one of: Co, Ni, Fe, or Heusler alloy. In some embodiments, the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V. In some embodiments, the method of forming the first and/or the third structures of the first and/or second magnetic junctions comprise forming a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy; and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni. In some embodiments, the method of forming the first and/or the third structures of the first and/or second magnetic junctions comprise forming a stack of three materials including a first material adjacent to the interconnect, a second material adjacent to the first material but not in contact with the interconnect, and third material adjacent to the second material and the second structure, wherein the first material includes one or more of: Co, Ni, Fe, or Heusler alloy, wherein the second material comprises Ru; and wherein the third material includes one or more of Co, Ni, Fe, or Heusler alloy.
[00166] Figs. 23A-B illustrate a 3D view 2300 and corresponding cross-section view 2330, respectively, of an oscillator having a magnetic junction with magnets having in-plane magnetizations, and a via having perpendicular magnet adjacent to the SOC interconnect, according to some embodiments of the disclosure. Figs. 23A-B is similar to Figs. 5A-B, respectively, but for different kinds of magnets. For example, magnetic junction 521 is replaced by magnetic junction 2351. Compared to magnetic junction 521, perpendicular free magnet 52laa is replaced with in-plane free magnet 232 laa, perpendicular free magnet 52 lab is replaced with in-plane free magnet 232 lab, and perpendicular fixed magnet 52 lac is replaced with in-plane fixed magnet 232lac. Further in-plane fixed magnet 534 is replaced by perpendicular fixed magnet 2334. Operation wise, the devices of Figs. 23A-B are similar to devices of Figs. 5A-B.
[00167] Figs. 24A-B illustrate a 3D view 2400 and corresponding cross-section view 2430, respectively, of an oscillator having a magnetic junction with magnets having in-plane magnetizations, and a via comprising perpendicular magnet and an anti-ferromagnet (AFM) one of which is adjacent to the SOC interconnect, according to some embodiments of the disclosure. Figs. 24A-B is similar to Figs. 6A-B, respectively, but for different kinds of magnets. For example, magnetic junction 521 is replaced by magnetic junction 2351.
Compared to magnetic junction 521, perpendicular free magnet 52laa is replaced with in plane free magnet 2321 aa, perpendicular free magnet 521 ab is replaced with in-plane free magnet 232lab, and perpendicular fixed magnet 52lac is replaced with in-plane fixed magnet 232 lac. Further in-plane fixed magnet 534 is replaced by perpendicular fixed magnet 2334 which is coupled to AFM 625. Operation wise, the devices of Figs. 24A-B are similar to devices of Figs. 5A-B.
[00168] Fig. 25 illustrates a smart device or a computer system or a SoC (System-on- Chip) 2300 with an SOT or SOC based oscillator, according to some embodiments of the disclosure.
[00169] For purposes of the embodiments, the transistors in various circuits and logic blocks described here are metal oxide semiconductor (MOS) transistors or their derivatives, where the MOS transistors include drain, source, gate, and bulk terminals. The transistors and/or the MOS transistor derivatives also include Tri-Gate and FinFET transistors, Gate All Around Cylindrical Transistors, Tunneling FET (TFET), Square Wire, or Rectangular Ribbon Transistors, ferroelectric FET (FeFETs), or other devices implementing transistor functionality like carbon nanotubes or spintronic devices. MOSFET symmetrical source and drain terminals i.e., are identical terminals and are interchangeably used here. A TFET device, on the other hand, has asymmetric Source and Drain terminals. Those skilled in the art will appreciate that other transistors, for example, Bi-polar junction transistors (BJT PNP/NPN), BiCMOS, CMOS, etc., may be used without departing from the scope of the disclosure.
[00170] Fig. 25 illustrates a block diagram of an embodiment of a mobile device in which flat surface interface connectors could be used. In some embodiments, computing device 1600 represents a mobile computing device, such as a computing tablet, a mobile phone or smart-phone, a wireless-enabled e-reader, or other wireless mobile device. It will be understood that certain components are shown generally, and not all components of such a device are shown in computing device 2300.
[00171] In some embodiments, computing device 2300 includes first processor 2310 with an SOT or SOC based oscillator, according to some embodiments discussed. Other blocks of the computing device 2300 may also include an SOT or SOC based oscillator, according to some embodiments. The various embodiments of the present disclosure may also comprise a network interface within 2370 such as a wireless interface so that a system embodiment may be incorporated into a wireless device, for example, cell phone or personal digital assistant.
[00172] In some embodiments, processor 2310 (and/or processor 2390) can include one or more physical devices, such as microprocessors, application processors,
microcontrollers, programmable logic devices, or other processing means. The processing operations performed by processor 2310 include the execution of an operating platform or operating system on which applications and/or device functions are executed. The processing operations include operations related to I/O (input/output) with a human user or with other devices, operations related to power management, and/or operations related to connecting the computing device 2300 to another device. The processing operations may also include operations related to audio I/O and/or display I/O.
[00173] In some embodiments, computing device 2300 includes audio subsystem 2320, which represents hardware (e.g., audio hardware and audio circuits) and software (e.g., drivers, codecs) components associated with providing audio functions to the computing device. Audio functions can include speaker and/or headphone output, as well as microphone input. Devices for such functions can be integrated into computing device 2300, or connected to the computing device 2300. In one embodiment, a user interacts with the computing device 2300 by providing audio commands that are received and processed by processor 2310.
[00174] In some embodiments, computing device 2300 comprises display subsystem 2330. Display subsystem 2330 represents hardware (e.g., display devices) and software (e.g., drivers) components that provide a visual and/or tactile display for a user to interact with the computing device 2300. Display subsystem 2330 includes display interface 2332, which includes the particular screen or hardware device used to provide a display to a user. In one embodiment, display interface 2332 includes logic separate from processor 2310 to perform at least some processing related to the display. In one embodiment, display subsystem 2330 includes a touch screen (or touch pad) device that provides both output and input to a user.
[00175] In some embodiments, computing device 2300 comprises I/O controller 2340. I/O controller 2340 represents hardware devices and software components related to interaction with a user. I/O controller 2340 is operable to manage hardware that is part of audio subsystem 2320 and/or display subsystem 2330. Additionally, I/O controller 2340 illustrates a connection point for additional devices that connect to computing device 2300 through which a user might interact with the system. For example, devices that can be attached to the computing device 2300 might include microphone devices, speaker or stereo systems, video systems or other display devices, keyboard or keypad devices, or other I/O devices for use with specific applications such as card readers or other devices.
[00176] As mentioned above, I/O controller 2340 can interact with audio subsystem 2320 and/or display subsystem 2330. For example, input through a microphone or other audio device can provide input or commands for one or more applications or functions of the computing device 2300. Additionally, audio output can be provided instead of, or in addition to display output. In another example, if display subsystem 2330 includes a touch screen, the display device also acts as an input device, which can be at least partially managed by I/O controller 2340. There can also be additional buttons or switches on the computing device 2300 to provide I/O functions managed by I/O controller 2340.
[00177] In some embodiments, I/O controller 2340 manages devices such as accelerometers, cameras, light sensors or other environmental sensors, or other hardware that can be included in the computing device 2300. The input can be part of direct user interaction, as well as providing environmental input to the system to influence its operations (such as filtering for noise, adjusting displays for brightness detection, applying a flash for a camera, or other features).
[00178] In some embodiments, computing device 2300 includes power management 2350 that manages battery power usage, charging of the battery, and features related to power saving operation. Memory subsystem 2360 includes memory devices for storing information in computing device 2300. Memory can include nonvolatile (state does not change if power to the memory device is interrupted) and/or volatile (state is indeterminate if power to the memory device is interrupted) memory devices. Memory subsystem 2360 can store application data, user data, music, photos, documents, or other data, as well as system data (whether long-term or temporary) related to the execution of the applications and functions of the computing device 2300.
[00179] Elements of embodiments are also provided as a machine-readable medium (e.g., memory 2360) for storing the computer-executable instructions (e.g., instructions to implement any other processes discussed herein). The machine-readable medium (e.g., memory 2360) may include, but is not limited to, flash memory, optical disks, CD-ROMs, DVD ROMs, RAMs, EPROMs, EEPROMs, magnetic or optical cards, phase change memory (PCM), or other types of machine-readable media suitable for storing electronic or computer- executable instructions. For example, embodiments of the disclosure may be downloaded as a computer program (e.g., BIOS) which may be transferred from a remote computer (e.g., a server) to a requesting computer (e.g., a client) by way of data signals via a communication link (e.g., a modem or network connection).
[00180] In some embodiments, computing device 2300 comprises connectivity 2370. Connectivity 2370 includes hardware devices (e.g., wireless and/or wired connectors and communication hardware) and software components (e.g., drivers, protocol stacks) to enable the computing device 2300 to communicate with external devices. The computing device 2300 could be separate devices, such as other computing devices, wireless access points or base stations, as well as peripherals such as headsets, printers, or other devices.
[00181] Connectivity 2370 can include multiple different types of connectivity. To generalize, the computing device 2300 is illustrated with cellular connectivity 2372 and wireless connectivity 2374. Cellular connectivity 2372 refers generally to cellular network connectivity provided by wireless carriers, such as provided via GSM (global system for mobile communications) or variations or derivatives, CDMA (code division multiple access) or variations or derivatives, TDM (time division multiplexing) or variations or derivatives, or other cellular service standards. Wireless connectivity (or wireless interface) 2374 refers to wireless connectivity that is not cellular, and can include personal area networks (such as Bluetooth, Near Field, etc.), local area networks (such as Wi-Fi), and/or wide area networks (such as WiMax), or other wireless communication.
[00182] In some embodiments, computing device 2300 comprises peripheral connections 2380. Peripheral connections 2380 include hardware interfaces and connectors, as well as software components (e.g., drivers, protocol stacks) to make peripheral connections. It will be understood that the computing device 2300 could both be a peripheral device ("to" 2382) to other computing devices, as well as have peripheral devices ("from" 2384) connected to it. The computing device 2300 commonly has a "docking" connector to connect to other computing devices for purposes such as managing (e.g., downloading and/or uploading, changing, synchronizing) content on computing device 2300. Additionally, a docking connector can allow computing device 2300 to connect to certain peripherals that allow the computing device 2300 to control content output, for example, to audiovisual or other systems.
[00183] In addition to a proprietary docking connector or other proprietary connection hardware, the computing device 2300 can make peripheral connections 2380 via common or standards-based connectors. Common types can include a Universal Serial Bus (USB) connector (which can include any of a number of different hardware interfaces), DisplayPort including MiniDisplayPort (MDP), High Definition Multimedia Interface (HDMI), Firewire, or other types.
[00184] Reference in the specification to "an embodiment," "one embodiment," "some embodiments," or "other embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments. The various appearances of "an embodiment," "one embodiment," or "some embodiments" are not necessarily all referring to the same embodiments. If the specification states a component, feature, structure, or characteristic "may," "might," or "could" be included, that particular component, feature, structure, or characteristic is not required to be included. If the specification or claim refers to "a" or "an" element, that does not mean there is only one of the elements. If the specification or claims refer to "an additional" element, that does not preclude there being more than one of the additional element.
[00185] Furthermore, the particular features, structures, functions, or characteristics may be combined in any suitable manner in one or more embodiments. For example, a first embodiment may be combined with a second embodiment anywhere the particular features, structures, functions, or characteristics associated with the two embodiments are not mutually exclusive.
[00186] While the disclosure has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations of such embodiments will be apparent to those of ordinary skill in the art in light of the foregoing description. The embodiments of the disclosure are intended to embrace all such alternatives, modifications, and variations as to fall within the broad scope of the appended claims.
[00187] In addition, well known power/ground connections to integrated circuit (IC) chips and other components may or may not be shown within the presented figures, for simplicity of illustration and discussion, and so as not to obscure the disclosure. Further, arrangements may be shown in block diagram form in order to avoid obscuring the disclosure, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements are highly dependent upon the platform within which the present disclosure is to be implemented (i.e., such specifics should be well within purview of one skilled in the art). Where specific details (e.g., circuits) are set forth in order to describe example embodiments of the disclosure, it should be apparent to one skilled in the art that the disclosure can be practiced without, or with variation of, these specific details. The description is thus to be regarded as illustrative instead of limiting. [00188] The following examples pertain to further embodiments. Specifics in the examples may be used anywhere in one or more embodiments. All optional features of the apparatus described herein may also be implemented with respect to a method or process.
[00189] Example 1. An apparatus comprising: a first magnetic junction; a second magnetic junction; an interconnect adjacent to the first and second magnetic junctions; a first structure adjacent to the interconnect such that the first structure is under the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device; and a second structure adjacent to the interconnect such that the second structure is under the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the plane of the device.
[00190] Example 2. The apparatus of example 1, wherein the interconnect comprises a first section and a section coupled to the first section via a conducting material.
[00191] Example 3. The apparatus of example 2, wherein the magnet of the first structure is adjacent to the first section, and wherein the magnet of the second structure is adjacent to the second section.
[00192] Example 4. The apparatus of example 2, wherein the first section or second section comprises an antiferromatic (AFM) material.
[00193] Example 5. The apparatus of example 4, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
[00194] Example 6. The apparatus of example 4, wherein the AFM material is a quasi- two-dimensional triangular AFM including Ni(i-X)MxGa2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
[00195] Example 7. The apparatus of example 2, wherein the first section or second section comprises: one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b-W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth or elements of 3d, 4d, 5d and 4f, 5f periodic groups, Ti, S, W, Mo, Se, B, Sb, Re, La, C, P, La, As, Sc, O, Bi,
Ga, Al, Y, In, Ce, Pr, Nd, F, Ir, Mn, Pd, or Fe.
[00196] Example 8. The apparatus of example 2, wherein the first section or second section comprises: spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material.
[00197] Example 9. The apparatus of example 2, wherein the first section or second section comprises: a spin orbit material which includes materials that exhibit Rashba- Bychkov effect. [00198] Example 10. The apparatus according to any one of preceding examples, wherein the first or second magnetic junctions is one of a spin valve or a magnetic tunneling junction (MTJ).
[00199] Example 11. The apparatus according to any one of examples 1 to 8, wherein the first or second magnetic junctions include: a stack of structures including: a first structure comprising a magnet with an unfixed perpendicular magnetic anisotropy (PMA) relative to the plane of the device; a second structure comprising one of a dielectric or metal; and a third structure comprising a magnet with fixed PMA relative to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations are in plane magnetizations.
[00200] Example 12. The apparatus according to any one of examples 1 to 8, wherein the first or second magnetic junctions include: a stack of structures including: a first structure comprising a magnet with an unfixed in-plane magnetic anisotropy relative to the plane of the device; a second structure comprising one of a dielectric or metal; a third structure comprising a magnet with fixed in-plane magnetic anisotropy relative to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations have perpendicular magnetic anisotropy (PMA).
[00201] Example 13. The apparatus of examples 11 or 12, wherein the magnetic junction comprises: a fourth structure between the first and second structures, wherein the fourth structure includes one or more of: Ru, Os, Hs, or Fe.
[00202] Example 14. The apparatus of examples 11 or 12, wherein the magnetic junction comprises a fifth structure between the second and third structures, wherein the fifth structure includes one or more of: Ru, Os, Hs, or Fe.
[00203] Example 15. The apparatus of example 2, wherein the first structure comprises an antiferromagnet (AFM) adjacent to the magnet of the first structure, and wherein the second structure comprises an AFM adjacent to the magnet of the second structure.
[00204] Example 16. The apparatus of example 2, wherein the fourth structure is between the interconnect and an eighth structure, wherein the eighth structure includes an antiferromagnet (AFM).
[00205] Example 17. The apparatus of examples 15 or 16, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe. [00206] Example 18. The apparatus of examples 15 or 16, wherein the AFM material is a quasi-two-dimensional triangular AFM including Ni(i-X)MxGa2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
[00207] Example 19. The apparatus of example 1, wherein the magnets of the first and/or second structures comprises one of: Co, Ni, Fe, or Heusler alloy.
[00208] Example 20. The apparatus of example 19, wherein the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
[00209] Example 21. The apparatus of examples 11 or 12, wherein the first and/or the third structures of the first and/or second magnetic junctions comprise a super lattice including a first material and a second material, wherein the first material includes one of:
Co, Ni, Fe, or Heusler alloy; and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
[00210] Example 22. The apparatus examples 11 or 12, wherein the first and/or the third structures of the first and/or second magnetic junctions comprise a stack of three materials including a first material adjacent to the interconnect, a second material adjacent to the first material but not in contact with the interconnect, and third material adjacent to the second material and the second structure, wherein the first material includes one or more of: Co, Ni, Fe, or Heusler alloy, wherein the second material comprises Ru; and wherein the third material includes one or more of Co, Ni, Fe, or Heusler alloy.
[00211] Example 23. A system comprising: a memory; a processor coupled to the memory, the processor having a spin wave switch, which comprises an apparatus according to any one of apparatus examples 1 to 22; and a wireless interface to allow the processor to communicate with another device.
[00212] Example 24. An apparatus comprising: an oscillator comprising an apparatus according to any one of examples 1 to 22; and circuitry to receive an output of the oscillator.
[00213] Example 25. An apparatus comprising: an array of antennas; and an array of oscillators with built-in mixers, wherein each antenna of the array of antennas is coupled to an oscillator forming a pair, wherein an individual oscillator comprises a spin orbit coupling material adjacent to a magnetic junction, and wherein at least one pair has an associated interconnect coupled to a corresponding Bias-T network.
[00214] Example 26. The apparatus of example 25, wherein at least one oscillator is to provide an oscillating output independent of an oscillating clock input.
[00215] Example 27. The apparatus of example 25 comprises: an array of isolators, wherein an individual isolator is coupled to the corresponding Bias-T network; and an array of filters, wherein an individual filter of the array of filters is coupled to the individual isolator of the array of isolators.
[00216] Example 28. The apparatus of example 25, wherein the array of antennas and the array of oscillators are configured as a space division multiplexed signal array.
[00217] Example 29. The apparatus of example 25, wherein the oscillator is according to any one of claims 1 to 22.
[00218] Example 30. An apparatus comprising: a parallel radio-frequency (RF) sensing array with a plurality of antennas, wherein an individual antenna is coupled to an oscillator according to any one apparatus examples 1 to 22.
[00219] Example 31. A method comprising: forming a first magnetic junction;
forming a second magnetic junction; forming an interconnect adjacent to the first and second magnetic junctions; forming a first structure adjacent to the interconnect such that the first structure is under the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device; and forming a second structure adjacent to the interconnect such that the second structure is under the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the plane of the device.
[00220] Example 32. The method of example 31, wherein forming the interconnect comprises forming a first section and a section coupled to the first section via a conducting material.
[00221] Example 33. The method of example 32, wherein the magnet of the first structure is adjacent to the first section, and wherein the magnet of the second structure is adjacent to the second section.
[00222] Example 34. The method of example 32, wherein the first section or second section comprises an antiferromatic (AFM) material.
[00223] Example 36. The method of example 34, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
[00224] Example 37. The method of example 34, wherein the AFM material is a quasi-two-dimensional triangular AFM including Ni(i-X)MxGa2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
[00225] Example 38. The method of example 32, wherein the first section or second section comprises: one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b-W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth or elements of 3d, 4d, 5d and 4f, 5f periodic groups, Ti, S, W, Mo, Se, B, Sb, Re, La, C, P, La, As, Sc, O, Bi,
Ga, Al, Y, In, Ce, Pr, Nd, F, Ir, Mn, Pd, or Fe.
[00226] Example 39. The method of example 32, wherein the first section or second section comprises: spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material.
[00227] Example 40. The method of example 32, wherein the first section or section comprises: a spin orbit material which includes materials that exhibit Rashba-Bychkov effect.
[00228] Example 41. The method according to any one of preceding method examples, wherein the first or second magnetic junctions is one of a spin valve or a magnetic tunneling junction (MTJ).
[00229] Example 42. The method according to any one of examples 31 to 38, wherein forming the first or second magnetic junctions include: forming a stack of structures including: forming a first structure comprising a magnet with an unfixed perpendicular magnetic anisotropy (PMA), wherein the first structure has an anisotropy axis perpendicular to the plane of the device; forming a second structure comprising one of a dielectric or metal; forming a third structure comprising a magnet with fixed PMA, wherein the third structure has an anisotropy axis perpendicular to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations are in-plane magnetizations.
[00230] Example 42. The method according to any one of examples 31 to 38, wherein forming the first or second magnetic junctions include: forming a stack of structures including: forming a first structure comprising a magnet with an unfixed in-plane magnetic anisotropy, wherein the first structure has an anisotropy axis along the plane of the device; forming a second structure comprising one of a dielectric or metal; forming a third structure comprising a magnet with fixed in-plane magnetic anisotropy, wherein the third structure has an anisotropy axis along the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures, wherein the first and second magnetizations have perpendicular magnetic anisotropy (PMA).
[00231] Example 43. The method of examples 41 or 42, wherein forming the magnetic junction comprises: forming a fourth structure between the first and second structures, wherein the fourth structure includes one or more of: Ru, Os, Hs, or Fe.
[00232] Example 44. The method of examples 41 or 42, wherein forming the magnetic junction comprises forming a fifth structure between the second and third structures, wherein the fifth structure includes one or more of: Ru, Os, Hs, or Fe. [00233] Example 45. The method of example 31, wherein forming the first structure comprises forming an antiferromagnet (AFM) adjacent to the magnet of the first structure, and wherein the second structure comprises an AFM adjacent to the magnet of the second structure.
[00234] Example 46. The method of example 31, wherein the fourth structure is between the interconnect and an eighth structure, wherein the eighth structure includes an antiferromagnet (AFM).
[00235] Example 47. The method of examples 45 or 46, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe.
[00236] Example 48. The method of claims 45 or 46, wherein the AFM material is a quasi-two-dimensional triangular AFM including Ni(i-X)MxGa2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
[00237] Example 49. The method of example 31, wherein the magnets of the first and/or second structures comprises one of: Co, Ni, Fe, or Heusler alloy.
[00238] Example 50. The method of example 49, wherein the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
[00239] Example 51. The method of examples 41 or 42, wherein forming the first and/or the third structures of the first and/or second magnetic junctions comprise forming a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy; and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
[00240] Example 52. The method of examples 41 or 42, wherein forming the first and/or the third structures of the first and/or second magnetic junctions comprise forming a stack of three materials including a first material adjacent to the interconnect, a second material adjacent to the first material but not in contact with the interconnect, and third material adjacent to the second material and the second structure, wherein the first material includes one or more of: Co, Ni, Fe, or Heusler alloy, wherein the second material comprises Ru; and wherein the third material includes one or more of Co, Ni, Fe, or Heusler alloy.
[00241] An abstract is provided that will allow the reader to ascertain the nature and gist of the technical disclosure. The abstract is submitted with the understanding that it will not be used to limit the scope or meaning of the claims. The following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separate embodiment.

Claims

CLAIMS We claim:
1. An apparatus comprising:
a first magnetic junction;
a second magnetic junction;
an interconnect adjacent to the first and second magnetic junctions;
a first structure adjacent to the interconnect such that the first structure is under the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device; and
a second structure adjacent to the interconnect such that the second structure is under the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the plane of the device.
2. The apparatus of claim 1, wherein the interconnect comprises a first section and a section coupled to the first section via a conducting material.
3. The apparatus of claim 2, wherein the magnet of the first structure is adjacent to the first section, and wherein the magnet of the second structure is adjacent to the second section.
4. The apparatus of claim 2, wherein the first section or second section comprises an
antiferromatic (AFM) material.
5. The apparatus of claim 4, wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe, or wherein the AFM material is a quasi-two-dimensional triangular AFM including Ni(i-X)MxGa2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
6. The apparatus of claim 2, wherein:
the first section or second section comprises: one or more or: b-Tantalum (b-Ta), Ta, b-Tungsten (b-W), W, Platinum (Pt), Copper (Cu) doped with elements including on of Iridium, Bismuth or elements of 3d, 4d, 5d and 4f, 5f periodic groups, Ti, S, W, Mo, Se, B, Sb, Re, La, C, P, La, As, Sc, O, Bi, Ga, Al, Y, In, Ce, Pr, Nd, F, Ir, Mn, Pd, or Fe; the first section or second section comprises: spin orbit material which includes one of a 2D material or a 3D material, wherein the 3D material is thinner than the 2D material; or
the first section or second section comprises: a spin orbit material which includes materials that exhibit Rashba-Bychkov effect.
7. The apparatus according to any one of preceding claims, wherein the first or second
magnetic junctions is one of a spin valve or a magnetic tunneling junction (MTJ).
8. The apparatus according to any one of claims 1 to 7, wherein the first or second magnetic junctions include: a stack of structures including:
a first structure comprising a magnet with an unfixed perpendicular magnetic anisotropy (PMA) relative to the plane of the device;
a second structure comprising one of a dielectric or metal; and
a third structure comprising a magnet with fixed PMA relative to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures,
wherein the first and second magnetizations are in-plane magnetizations.
9. The apparatus according to any one of claims 1 to 7, wherein the first or second magnetic junctions include: a stack of structures including:
a first structure comprising a magnet with an unfixed in-plane magnetic anisotropy relative to the plane of the device;
a second structure comprising one of a dielectric or metal;
a third structure comprising a magnet with fixed in-plane magnetic anisotropy relative to the plane of the device, and wherein the third structure is adjacent to the second structure such that the second structure is between the first and third structures,
wherein the first and second magnetizations have perpendicular magnetic anisotropy (PMA).
10. The apparatus of claims 8 or 9, wherein the magnetic junction comprises: a fourth
structure between the first and second structures, wherein the fourth structure includes one or more of: Ru, Os, Hs, or Fe.
11. The apparatus of claims 8 or 9, wherein the magnetic junction comprises a fifth structure between the second and third structures, wherein the fifth structure includes one or more of: Ru, Os, Hs, or Fe.
12. The apparatus of claim 2, wherein the first structure comprises an antiferromagnet (AFM) adjacent to the magnet of the first structure, and wherein the second structure comprises an AFM adjacent to the magnet of the second structure.
13. The apparatus of claim 2, wherein the fourth structure is between the interconnect and an eighth structure, wherein the eighth structure includes an antiferromagnet (AFM), wherein the AFM material includes one of: Ir, Pt, Mn, Pd, or Fe, or wherein the AFM material is a quasi-two-dimensional triangular AFM including Ni(i-X)MxGa2S4, where‘M’ includes one of: Mn, Fe, Co or Zn.
14. The apparatus of claim 1, wherein the magnets of the first and/or second structures
comprises one of: Co, Ni, Fe, or Heusler alloy, and wherein the Heusler alloy includes one or more of Co, Cu, Fe, Ga, Ge, In, Mn, Al, In, Sb, Si, Sn, Ni, Pd, Ru, or V.
15. The apparatus of claims 8 or 9, wherein the first and/or the third structures of the first and/or second magnetic junctions comprise a super lattice including a first material and a second material, wherein the first material includes one of: Co, Ni, Fe, or Heusler alloy; and wherein the second material includes one of: Pt, Pd, Ir, Ru, or Ni.
16. The apparatus claims 8 or 9, wherein the first and/or the third structures of the first and/or second magnetic junctions comprise a stack of three materials including a first material adjacent to the interconnect, a second material adjacent to the first material but not in contact with the interconnect, and third material adjacent to the second material and the second structure, wherein the first material includes one or more of: Co, Ni, Fe, or Heusler alloy, wherein the second material comprises Ru; and wherein the third material includes one or more of Co, Ni, Fe, or Heusler alloy.
17. A system comprising: a memory; a processor coupled to the memory, the processor having a spin wave switch, which comprises an apparatus according to any one of apparatus claims 1 to 16; and a wireless interface to allow the processor to communicate with another device.
18. An apparatus comprising:
an oscillator comprising an apparatus according to any one of claims 1 to 16; and circuitry to receive an output of the oscillator.
19. An apparatus comprising:
an array of antennas; and
an array of oscillators with built-in mixers, wherein each antenna of the array of antennas is coupled to an oscillator forming a pair, wherein an individual oscillator comprises a spin orbit coupling material adjacent to a magnetic junction, and wherein at least one pair has an associated interconnect coupled to a corresponding Bias-T network.
20. The apparatus of claim 19, wherein at least one oscillator is to provide an oscillating output independent of an oscillating clock input.
21. The apparatus of claim 19 comprises:
an array of isolators, wherein an individual isolator is coupled to the corresponding Bias-T network; and
an array of filters, wherein an individual filter of the array of filters is coupled to the individual isolator of the array of isolators.
22. The apparatus of claim 19, wherein the array of antennas and the array of oscillators are configured as a space division multiplexed signal array.
23. The apparatus of claim 20, wherein the oscillator is according to any one of claims 1 to 16.
24. An apparatus comprising:
a parallel radio-frequency (RF) sensing array with a plurality of antennas, wherein an individual antenna is coupled to an oscillator according to any one apparatus claims 1 to 16.
25. A method comprising:
forming a first magnetic junction; forming a second magnetic junction;
forming an interconnect adjacent to the first and second magnetic junctions; forming a first structure adjacent to the interconnect such that the first structure is under the first magnetic junction, wherein the first structure comprises a magnet with a first magnetization relative to a plane of a device; and
forming a second structure adjacent to the interconnect such that the second structure is under the second magnetic junction, wherein the second structure comprises a magnet with a second magnetization relative to the plane of the device.
PCT/US2017/067106 2017-12-18 2017-12-18 Spin orbit coupling based oscillator using exchange bias WO2019125388A1 (en)

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