WO2017105396A1

WO2017105396A1 - Magnetoelectric oscillatory cellular neural network apparatus and method

Info

Publication number: WO2017105396A1
Application number: PCT/US2015/065618
Authority: WO
Inventors: Dmitri E. Nikonov; Sasikanth Manipatruni; Ian A. Young
Original assignee: Intel Corp
Current assignee: Intel Corp
Priority date: 2015-12-14
Filing date: 2015-12-14
Publication date: 2017-06-22
Anticipated expiration: 2018-06-14

Abstract

Described is an apparatus which comprises: a network of magnetic interconnects; a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects; and a plurality of oscillators positioned at cross-points of the network of magnetic interconnects. Described is a method which comprises: applying an AC voltage to a plurality of oscillators positioned at cross-points of a network of magnetic interconnects; and applying a DC voltage to a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects.

Description

MAGNETOELECTRIC OSCILLATORY CELLULAR NEURAL NETWORK

APPARATUS AND METHOD

BACKGROUND

[0001] Cellular Neural Networks (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 resistor-inductor-capacitor (RLC) oscillators as shown in Fig. 1.

[0002] Fig. 1 illustrates scheme 100 of an oscillatory CNN where each oscillator

(OSC) is an RLC network. The OSCs are coupled together via inductors L0. In this example, an NxN array of OSCs are shown, where each OSC is a cell or neuron, and where 'N' is an integer. Scheme 100 results in a very large CNN because of the large sizes for resistors, inductors, and capacitors. Such CNNs are not suitable for small form factor processors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0003] 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.

[0004] Fig. 1 illustrates a traditional scheme of an oscillatory Cellular Neural

Network (CNN).

[0005] Fig. 2 illustrates a magnetic oscillatory CNN, in accordance with some embodiments.

[0006] Fig. 3 illustrates a magnetostrictive cell used as an oscillator for the magnetic oscillatory CNN, in accordance with some embodiments.

[0007] Fig. 4 illustrates a magnetic tunneling junction (MTJ) cell used as an oscillator for the magnetic oscillatory CNN, in accordance with some embodiments.

[0008] Fig. 5 illustrates a flowchart of a method for enabling a magnetic oscillatory

CNN having magnetostrictive cells as oscillators, in accordance with some embodiments. [0009] Fig. 6 illustrates a flowchart of a method for enabling a magnetic oscillatory

CNN having MTJ cells as oscillators, in accordance with some embodiments.

[0010] Fig. 7 illustrates a smart device or a computer system or a SoC (System-on-

Chip) with a magnetic oscillatory CNN, according to some embodiments.

DETAILED DESCRIPTION

[0011] Various embodiments describe an array of compact oscillators configured as a

Cellular Neural Network (CNN). In some embodiments, the oscillators are implemented as magnetostrictive cells. In some embodiments, the oscillators are implemented as Spin Transfer Torque (STT) based cells such as Magnetic Tunneling Junctions (MTJs) or spin valves. In some embodiments, the oscillators are placed on cross-points or intersections of a magnetic grid. In some embodiments, phase-shifters (or phase couplers) and oscillators are dispersed between successive oscillators to change the phase of spin waves travelling through the magnetic grid.

[0012] There are many technical effects or benefits of the various embodiments. For example, the oscillators are much more compact than the RLC based oscillators of Fig. 1. In some embodiments, the oscillators may be formed by a single magnetoelectric cell. In some embodiments, a single magnetoelectric cell is used per phase coupler. In some embodiments, the phase couplers are reconfigurable that allows for a variety of more processing

capabilities. For example, the phase couplers can change the phase of the spin waves in the magnetic grid in a controlled fashion. The CNN described with reference to various embodiments is magnetic (e.g., states of coupling magnetoelectric cells are non-volatile). As such, in some embodiments, the array of compact oscillators can be field programmed and trained for machine learning.

[0013] 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.

[0014] 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.

[0015] 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. 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. 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. 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."

[0016] The terms "substantially," "close," "approximately," "near," and "about," generally refer to being within +/- 10% of a target value (unless specifically specified). 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.

[0017] 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). 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.

[0018] 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.

[0019] Fig. 2 illustrates magnetic oscillatory CNN 200, in accordance with some embodiments. In some embodiments, CNN 200 comprises phase shifter and attenuator 201 (or phase coupler), oscillator 202, and magnetic grid or interconnect 203.

[0020] In some embodiments, phase shifter and attenuator 201 is placed between two oscillators 202. In some embodiments, phase shifter and attenuator 201 is placed above a portion of magnetic grid or interconnect 203 such that phase shifter and attenuator 201 couples the portion of magnetic grid or interconnect 203. In some embodiments, phase shifter and attenuator 201 is a magnetostrictive device which is operable to change the phase of spin waves traversing through magnetic grid or interconnect 203 in contact with phase shifter and attenuator 201. As such, the phase of coupling is adjusted.

[0021] In some embodiments, phase shifter and attenuator 201 has the structure 300 shown in Fig. 3 and comprises a portion of magnetic grid 203 (a first ferromagnetic (FM) layer, e.g., comprising alloys of Co, Fe, Ni, or B), a piezoelectric (Pze) material 301, and the metallic contact 302. In some embodiments, oscillator 202 also has a structure same that describd with reference to Fig. 3. In some embodiments, FM layer 203 is connected to electrical ground. In some embodiments, DC voltage 303 is applied to Contact 302. As a result, strain is applied from Pze material layer 301 to FM layer 203, and therefore its magnetic anisotropy changes, which leads to a change of phase and amplitude of spin waves travelling in FM layer 203.

[0022] In some embodiments, AC voltage is applied to Contact 303, and the variable strain and magnetic anisotropy change the phase and amplitude of spin waves in FM layer 203. Referring back to Fig. 2, in some embodiments, phase shifter and attenuator 201 has the structure 400 shown in Fig. 4. In some embodiments, oscillator 202 also has a structure same that describd with reference to Fig. 4. In some embodiments, phase shifter and attenuator 201 comprises a first ferromagnetic layer 203 (e.g., layer comprising alloys of Co, Fe, Ni, or B); a second layer 401 (e.g., layer of MgO or other insulating oxide layers, such as AI2O3); third FM layer 402; and a fourth layer 403 (e.g., Contact layer of Ta or Cu). In some embodiments, phase shifter and attenuator 201 comprises ferromagnetic layer 402, the magnetization of which may be fixed. [0023] While the materials listed for first FM layer 203 are used in some

embodiments, in other embodiments other elements or compounds that can change the phase of spin wave with or without application of an external voltage may be used for forming the first layer of phase shifter and attenuator 201. For example, Yttrium Iron Garnet (YIG), or a combination of YIG with other elements or compounds can be used for forming the first layer of phase shifter and attenuator 201. In some embodiments, first and third FM layers 203 and 402, respectively, are formed of Heusler alloys which are one of: Cu₂MnAl, Cu₂MnIn, Cu₂MnSn, Ni₂MnAl, Ni₂MnIn, Ni₂MnSn, Ni₂MnSb, Ni₂MnGa Co₂MnAl, Co₂MnSi,

Co₂MnGa, CoJVInGe, Pd₂MnAl, PdJVInln, Pd₂MnSn, Pd₂MnSb, Co₂FeSi, Co₂FeAl, Fe₂VAl, Mn₂VGa, Co₂FeGe, MnGa, or MnGaRu).

[0024] In some embodiments, fourth layer 403 forms a contact for coupling to voltage source 404. In some embodiments, second layer 401 of phase shifter and attenuator 201 is sandwiched between first and third FM layers (e.g., FM layer 203 and FM layer 202). In some embodiments, when voltage is applied to contact 403, the surface anisotropy changes at the interface between FM layer 203 and second layer 401. As such, the phase and amplitude of spin waves travelling in FM layer 203 change as well, in accordance with some embodiments.

[0025] Referring back to Fig. 2, in some embodiments, the first layer of phase shifter and attenuator 201 is coupled to the portion of magnetic grid or interconnect 203. In some embodiments, CNN 200 comprises a voltage source coupled to phase shifter and attenuator 201. In some embodiments, the voltage source is operable to adjust a coupling coefficient of phase shifter and attenuator 201 by applying a voltage on a third layer (e.g., contract layer 302 or 403 with reference to Figs. 3-4, respectively). Referring back to Fig. 2, in some embodiments, phase shifter and attenuator 201 are placed between successive oscillators 202.

[0026] In some embodiments, oscillator 202 is a magnetoelectric cell (also referred to as magnetoelectric oscillator 202). In some embodiments, oscillator 202 is placed at cross- points or intersections of magnetic grid or interconnect 203. In some embodiments, magnetoelectric oscillator 202 has the structure shown in Fig. 3 and comprises: a

piezoelectric (PZe) layer 301 coupled to a portion of magnetic grid or interconnect 203; and a non-magnetic contact layer 302 coupled to the PZe layer 301. In some embodiments, the PZe layer 301 provides a piezoelectric effect upon applied voltage by voltage source 303. In some embodiments, when AC voltage from voltage source 303 is applied to the PZe layer 301, a strain is created which changes the magnetic anisotropy of the portion of magnet of magnetic grid or interconnect 203 coupled to the PZe layer 301. The change in the magnetic anisotropy causes the magnetization of the portion of magnet 203 to oscillate (e.g., between in-plane and out-of-plane directions).

[0027] Referring back to Fig. 2, the oscillation in magnetization causes spin waves

204 to propagate through the magnetic grid or interconnect 203, in accordance with some embodiments. In some embodiments, CNN 200 comprises a voltage source which is operable to apply an AC voltage to the non-magnetic layer. In some embodiments, the frequency of the AC voltage affects the oscillating frequency of magnetoelectric oscillator 202. In some embodiments, the oscillating frequency of magnetoelectric oscillator 202 is a harmonic of the frequency of the applied AC voltage.

[0028] In some embodiments, spin torque oscillator (STO) 202 has the structure shown in Fig. 4. In some embodiments, STO 202 comprises a first ferromagnetic layer 203 (e.g., layer comprising alloys of Co, Fe, Ni, or B); a second layer 401 (e.g., layer of MgO or other insulating oxide layers, such as AI2O3); a third layer (e.g., FM layer 402) and a foruth layer 403 (e.g., layer of Ta or Cu). In some embodiments, voltage from voltage source 404 is applied to Contact 403 and causes DC current to flow to electrical ground attached to FM layer 203.

[0029] In some embodiments, STO oscillator 202 comprises a magnetic junction between FM layers 203 and 402. In some embodiments, the magnetic junction is one of a spin valve. In one such embodiments, layer 401 is a metal layer. In some embodiments, the magnetic junction is a magnetic tunneling junction (MTJ). In one such embodiment, layer 401 is an insulating layer e.g., MgO.

[0030] Referring back to Fig. 2, in some embodiments, CNN 200 comprises a current source which is operable to apply a DC current to the magnetic junction. This leads to the effect of spin transfer torque (STT) acting on layer 203 and causing magnetization in it to oscillate, in accordance with some embodiments. As such, the magnetic junction oscillates and generates spin waves in the four directions on the four portions of magnetic grid or interconnect 203 coupled to STT oscillator 202.

[0031] In some embodiments, magnetic grid or interconnect 203 is a free magnetic layer. The thickness of a ferromagnetic layer may determine its magnetization direction. For example, when the thickness of the ferromagnetic layer is above a certain threshold

(depending on the material of the magnet, e.g. approximately 1.5nm for CoFe), then the ferromagnetic layer exhibits magnetization direction which is in-plane. Likewise, when the thickness of the ferromagnetic layer is below a certain threshold (depending on the material of the magnet), then the ferromagnetic layer exhibits magnetization direction which is perpendicular to the plane of the magnetic layer. Other factors may also determine the direction of magnetization.

[0032] 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 cube), BCC (body centered cube), or LlO-type of crystals, where LI 0 is a type of crystal class which exhibits perpendicular magnetizations), can also determine the direction of magnetization.

[0033] In some embodiments, magnetic grid or interconnect 203 is made from CFGG

(i.e., Cobalt (Co), Iron (Fe), Germanium (Ge), or Gallium (Ga) or a combination of them). In some embodiments, magnetic grid or interconnect 203 is 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.

[0034] In some embodiments, magnetic grid or interconnect 203 is formed of one of:

Heusler alloy, Co, Fe, Ni, Gd, B, Ge, Ga, permalloy (e.g., NiFe alloy), Yttrium Iron Garnet (YIG), or a combination of them. In some embodiments, Heusler alloys are one of:

CiteMnAl, Cu₂MnIn, Cu₂MnSn, Ni₂MnAl, Ni₂MnIn, Ni₂MnSn, Ni₂MnSb, Ni₂MnGa

Co₂MnAl, Co₂MnSi, Co₂MnGa, Co₂MnGe, Pd₂MnAl, Pd₂MnIn, Pd₂MnSn, Pd₂MnSb, Co₂FeSi, Co₂FeAl, Fe₂VAl, Mn₂VGa, Co₂FeGe, MnGa, or MnGaRu.

[0035] In some embodiments, the magnets of magnetic grid or interconnect 203 are formed with a sufficiently high anisotropy (Hk) and sufficiently low magnetic saturation (M_s) to increase injection of spin currents. Magnetic saturation M_s is generally the state reached when an increase in applied external magnetic field H cannot increase the magnetization of the material (i.e., total magnetic flux density B substantially levels off). Here, sufficiently low Ms refers to M_s less than 200 kA/m (kilo-Amperes per meter). Anisotropy Hk generally refers to the material property which is directionally dependent. Materials with high Hk are materials with material properties that are highly directionally dependent. Here, sufficiently high Hk in context of Heusler alloys is considered to be greater than 2000 Oe (Oersted).

[0036] In some embodiments, magnetic grid or interconnect 203 is formed as a square or rectangular mesh. In other embodiments, other topologies may be formed. In some embodiments, oscillators 202 are defined in a normed space (e.g., a two-dimensional Euclidean geometry), like a grid. In some embodiments, oscillators 202 are not limited to two-dimensional spaces. For example, oscillators 202 can be defined in arbitrary numbers of dimensions such as: square, triangle, hexagonal, or any other spatially invariant arrangement. In some embodiment, topologically, oscillators 202 can be arranged on an infinite plane or on a toroidal space. In some embodiments, the magnetic interconnect 203 is local (i.e., all connections between oscillators 202 are within a specified radius, where distance is measured topologically). In some embodiments, the oscillating magnetization generated by oscillators 202 at the cross-point leads to spin waves (i.e., travelling magnetization perturbation) propagating along magnetic interconnect 203 (i.e., ferromagnetic wires).

[0037] Fig. 3 illustrates magnetostrictive cell (or oscillator) 300/202 used as an oscillator for magnetic oscillatory CNN 200, in accordance with some embodiments. It is pointed out that those elements of Fig. 3 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. As described with reference to Fig. 2, magnetostrictive cell 300 can also be used as phase shifter and attenuator 201.

[0038] In some embodiments, magnetostrictive cell 300 comprises PZe layer 301 and contact 302. In some embodiments, a voltage source 303 is provided which is coupled to contact 302. In some embodiments, PZe layer 301 is coupled to magnetic interconnect 203. In some embodiments, Piezoelectric layer 301 is formed of poly crystalline ferroelectric ceramics. In some embodiments, PZe layer 301 is formed of: lead zirconate titanate (PZT) Pb[Zr_xTii._x]0₃; barium titanate (BTO) BaTiC ; CoFeO. In other embodiments, other materials may be used for forming PZe layer 301. For example, materials such as PZT-5, PZT-4, PZNPT, PMNPT, BiFeOs; Bi₄Ti30i₂; Polyvinylidene fluoride, and PVDF can be used for forming Piezoelectric layer 301. In some embodiments, contact 302 is any non-magnetic metal (e.g., Cu).

[0039] Fig. 4 illustrates MTJ cell 400/202 used as an oscillator for magnetic oscillatory CNN 200, in accordance with some embodiments. It is pointed out that those elements of Fig. 4 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. Here, MTJ cell 400/202 is also referred to as oscillator 400/202. As described with reference to Fig. 4, magnetostrictive cell 400 can also be used as phase shifter and attenuator 201.

[0040] In some embodiments, oscillator 400/202 comprises stacking of a

ferromagnetic (FM) layer 203 (e.g., Free Magnet) with a tunneling dielectric 401 (e.g., MgO) and another ferromagnetic layer 402 (e.g., Fixed Magnet). A wide combination of materials can be used for material stacking of MTJ 400/202. For example, the stack of materials include: Co_xFeyB_z, MgO, Co_xFeyB_z, Ru, Co_xFeyB_z, IrMn, Ru, Ta, and Ru, where 'x,' 'y,' and 'z' are fractions of elements in the alloys. In some embodiments, fixed magnetic layer 402 may be a combination of CoFe, Ru, and CoFe layers referred to as Synthetic Anti- Ferromagnet (SAF) - based, and an Anti-Ferromagnet (AFM) layer.

[0041] In some embodiments, oscillator 400/202 includes a magnetic junction having free 203 and fixed magnetic 402 layers such that one of the magnetic layers is an in-plane magnet and another is a perpendicular magnet. As such, the magnetization direction of the fixed magnetic layer 402 is perpendicular relative to the magnetization direction of the free magnetic layer 203 (i.e., magnetization directions of the free and fixed magnetic layers are not parallel, rather they are orthogonal).

[0042] For example, the magnetization direction of the free magnetic layer 203 is in- plane while the magnetization direction of the fixed magnetic layer 402 is perpendicular to the in-plane. In another case, the magnetization direction of the fixed magnetic layer 402 is in-plane while the magnetization direction of the free magnetic layer 203 is perpendicular to the in-plane. The thickness of a ferromagnetic layer (i.e., fixed or free magnetic layer) may determine its magnetization direction.

[0043] For example, when the thickness of the ferromagnetic layer is above a certain threshold (depending on the material of the magnet, e.g. approximately 1.5nm for CoFe), then the ferromagnetic layer exhibits magnetization direction which is in-plane. Likewise, when the thickness of the ferromagnetic layer is below a certain threshold (depending on the material of the magnet), then the ferromagnetic layer exhibits magnetization direction which is perpendicular to the plane of the magnetic layer. Other factors may also determine the direction of magnetization.

[0044] 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, BCC, or L10- type of crystals, where L10 is a type of crystal class which exhibits perpendicular magnetizations), can also determine the direction of magnetization.

[0045] In some embodiments, fixed magnetic 402 layer is made from CFGG (i.e.,

Cobalt (Co), Iron (Fe), Germanium (Ge), or Gallium (Ga) or a combination of them). In some embodiments, fixed magnetic 402 layer is formed from Heusler alloys. In some embodiments, fixed magnetic 402 layer is formed of one of: Heusler alloy, Co, Fe, Ni, Gd, B, Ge, Ga, permalloy, Yttrium Iron Garnet (YIG), or a combination of them. In some embodiments, Heusler alloys are 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.

[0046] In some embodiments, the magnet (e.g., fixed magnetic layer 402) with perpendicular magnetic anisotropy (PMA) is formed form multiple layers in a stack (i.e., perpendicular magnetic layer is formed of multiple layers). The multiple thin layers can be layers of Cobalt and Platinum (i.e., Co/Pt), for example. Other examples of the multiple thin layers include: 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, MgO; Mn_xGa_y; Materials with L10 crystal symmetry; or materials with tetragonal crystal structure. In some embodiments, the perpendicular magnetic layer is formed of a single layer of one or more materials. In some embodiments, the single layer is formed of MnGa. In some embodiments, the perpendicular magnetic layer is formed of one of: a Heusler alloy, Co, Fe, Ni, Gd, B, Ge, Ga, or a combination of them.

[0047] In some embodiments, the free 203 and fixed 402 magnetic layers are separated by a metal 401. In one such embodiment, the magnetic junction is a spin valve. In some embodiments, the free 203 and fixed 402 magnetic layers are separated by a dielectric (e.g., MgO). In one such embodiment, the magnetic junction is a magnetic tunneling junction (MTJ).

[0048] In some embodiments, oscillator 400/202 includes a spin orbit coupling (SOC) layer (not shown) coupled to free magnet 203 of the magnetic junction. In some

embodiments, the SOC layer is operable to exhibit spin Hall effect (SHE). In some embodiments, the SOC layer is made of one or more of β-Tantalum (β-Ta), Ta, β-Tungsten (β-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, 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 oscillator 400/202. In some embodiments, CNN 200 comprises current source 404 which is coupled to contact 403. In some embodiments, current source 404 is to apply a DC current to the fixed magnet 402. In some embodiments, when DC current flows through the stack, it causes spin waves to be generated on FM 203. [0049] Fig. 5 illustrates flowchart 500 of a method for enabling a magnetic oscillatory

CNN 200 having magnetostrictive cells as oscillators 202, in accordance with some embodiments. It is pointed out that those elements of Fig. 5 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.

[0050] Although the blocks in the flowchart with reference to Fig. 5 are shown in a particular order, the order of the actions can be modified. Thus, the illustrated embodiments can be performed in a different order, and some actions/blocks may be performed in parallel. Some of the blocks and/or operations listed in Fig. 5 are optional in accordance with certain embodiments. The numbering of the blocks presented is for the sake of clarity and is not intended to prescribe an order of operations in which the various blocks must occur.

Additionally, operations from the various flows may be utilized in a variety of combinations.

[0051] At block 501, an AC voltage is applied to a plurality of oscillators 202 positioned at cross-points of the network of magnetic interconnects 203. Depending on the frequency of the AC voltage, plurality of oscillators 202 generate spin waves. These spin waves propagate via magnetic interconnects 203 away from the oscillators towards phase couplers 201. At block 502, a DC voltage is applied to a plurality of phase shifters and attenuators (same as phase couplers 201) coupled to the network of magnetic interconnects. In some embodiments, phase couplers 201 allow propagation of the spin waves such that input spin waves have different phase that output spin waves.

[0052] In some embodiments, an array of data (e.g., an image) is loaded into CNN

200 and encoded as initial phases of oscillators and (in general time-dependent) values of driving voltages of currents. In some embodiments, the change of phase corresponds to a change of coupling coefficients between the magnetizations of oscillators 202. Various data processing algorithms can be implemented as various combinations of these coupling coefficients, in accordance with some embodiments.

[0053] Fig. 6 illustrates flowchart 600 of a method for enabling a magnetic oscillatory

CNN 200 having MTJ cells as oscillators 202, in accordance with some embodiments. It is pointed out that those elements of Fig. 6 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.

[0054] Although the blocks in the flowchart with reference to Fig. 6 are shown in a particular order, the order of the actions can be modified. Thus, the illustrated embodiments can be performed in a different order, and some actions/blocks may be performed in parallel. Some of the blocks and/or operations listed in Fig. 6 are optional in accordance with certain embodiments. The numbering of the blocks presented is for the sake of clarity and is not intended to prescribe an order of operations in which the various blocks must occur.

[0055] At block 601, a DC current is applied to a plurality of oscillators 400/202 positioned at cross-points of the network of magnetic interconnects 203. Depending on the bias voltage and thus current in the SOC layer discussed with reference to Fig. 4, plurality of oscillators 202 generate spin waves of certain frequency. The oscillating frequency can be changed by changing the bias voltage to the SOC layer. These spin waves propagate via magnetic interconnects 203 away from the oscillators towards phase couplers 201. At block 602, DC voltage is applied to a plurality of phase shifters and attenuators 201 coupled to the network of magnetic interconnects 203. In some embodiments, phase couplers 201 allow propagation of the spin waves such that input spin waves have different phase that output spin waves.

[0056] In some embodiments, an array of data (e.g., an image) is loaded into CNN

[0057] Fig. 7 illustrates a smart device or a computer system or a SoC (System-on-

Chip) with a magnetic oscillatory CNN, according to some embodiments. It is pointed out that those elements of Fig. 7 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.

[0058] Fig. 7 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 1600.

[0059] In some embodiments, computing device 1600 includes first processor 1610 with a magnetic oscillatory CNN, according to some embodiments discussed. Other blocks of the computing device 1600 may also include the magnetic oscillatory CNN, according to some embodiments. The various embodiments of the present disclosure may also comprise a network interface within 1670 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.

[0060] In some embodiments, processor 1610 (and/or processor 1690) 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 1610 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 1600 to another device. The processing operations may also include operations related to audio I/O and/or display I/O.

[0061] In some embodiments, computing device 1600 includes audio subsystem

1620, 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 1600, or connected to the computing device 1600. In one embodiment, a user interacts with the computing device 1600 by providing audio commands that are received and processed by processor 1610.

[0062] In some embodiments, computing device 1600 comprises display subsystem

1630. Display subsystem 1630 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 1600. Display subsystem 1630 includes display interface 1632, which includes the particular screen or hardware device used to provide a display to a user. In one embodiment, display interface 1632 includes logic separate from processor 1610 to perform at least some processing related to the display. In one embodiment, display subsystem 1630 includes a touch screen (or touch pad) device that provides both output and input to a user.

[0063] In some embodiments, computing device 1600 comprises I/O controller 1640.

I/O controller 1640 represents hardware devices and software components related to interaction with a user. I/O controller 1640 is operable to manage hardware that is part of audio subsystem 1620 and/or display subsystem 1630. Additionally, I/O controller 1640 illustrates a connection point for additional devices that connect to computing device 1600 through which a user might interact with the system. For example, devices that can be attached to the computing device 1600 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.

[0064] As mentioned above, I/O controller 1640 can interact with audio subsystem

1620 and/or display subsystem 1630. 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 1600. Additionally, audio output can be provided instead of, or in addition to display output. In another example, if display subsystem 1630 includes a touch screen, the display device also acts as an input device, which can be at least partially managed by I/O controller 1640. There can also be additional buttons or switches on the computing device 1600 to provide I/O functions managed by I/O controller 1640.

[0065] In some embodiments, I/O controller 1640 manages devices such as accelerometers, cameras, light sensors or other environmental sensors, or other hardware that can be included in the computing device 1600. 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).

[0066] In some embodiments, computing device 1600 includes power management

1650 that manages battery power usage, charging of the battery, and features related to power saving operation. Memory subsystem 1660 includes memory devices for storing information in computing device 1600. 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 1660 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 1600. In some embodiments, Memory subsystem 1660 includes the scheme of analog in-memory partem matching with the use of resistive memory elements.

[0067] Elements of embodiments are also provided as a machine-readable medium

(e.g., memory 1660) for storing the computer-executable instructions (e.g., instructions to implement any other processes discussed herein). The machine-readable medium (e.g., memory 1660) 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).

[0068] In some embodiments, computing device 1600 comprises connectivity 1670.

Connectivity 1670 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 1600 to communicate with external devices. The computing device 1600 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.

[0069] Connectivity 1670 can include multiple different types of connectivity. To generalize, the computing device 1600 is illustrated with cellular connectivity 1672 and wireless connectivity 1674. Cellular connectivity 1672 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) 1674 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. In some embodiments, Connectivity 1670 includes parallel sensing arrays as described with reference to Figs. 10-13.

[0070] In some embodiments, computing device 1600 comprises peripheral connections 1680. Peripheral connections 1680 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 1600 could both be a peripheral device ("to" 1682) to other computing devices, as well as have peripheral devices ("from" 1684) connected to it. The computing device 1600 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 1600. Additionally, a docking connector can allow computing device 1600 to connect to certain peripherals that allow the computing device 1600 to control content output, for example, to audiovisual or other systems.

[0071] In addition to a proprietary docking connector or other proprietary connection hardware, the computing device 1600 can make peripheral connections 1680 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] For example, an apparatus is provided: a network of magnetic interconnects; a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects; and a plurality of oscillators positioned at cross-points of the network of magnetic interconnects. In some embodiments, at least one of the oscillators of the plurality of oscillators is a magnetostrictive device. In some embodiments, the magnetostrictive device comprises: a piezoelectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and a non-magnetic layer coupled to the piezoelectric layer. In some embodiments, the piezoelectric layer is formed of one of: lead zirconate titanate (PZT) Pb[Zr_rTi_{l r}]0₃; barium titanate (BTO) BaTi0₃; CoFeO, PZT-5, PZT-4, PZNPT, PMNPT, BiFeC ; Bi4Ti30i2; Polyvinylidene fluoride, or PVDF. In some embodiments, the apparatus comprises a voltage source which is to apply an AC voltage to the non-magnetic layer. In some embodiments, at least one of the oscillators of the plurality of oscillators is a spin transfer torque (STT) device. In some embodiments, the STT device comprises a magnetic junction.

[0078] In some embodiments, the magnetic junction is one of a spin valve or a magnetic tunneling junction (MTJ). In some embodiments, the STT device comprises: a dielectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and a fixed magnet coupled to the dielectric layer. In some embodiments, the dielectric layer is MgO. In some embodiments, the apparatus comprises a current source which is to apply a DC current to the fixed magnet. In some embodiments, at least one of the phase shifter and attenuator of the plurality of phase shifters and attenuators comprises: a layer comprising alloys of Co, Fe, Ni, or B; a layer of MgO; and a layer of Ta or Cu. In some embodiments, the apparatus comprises a voltage source coupled to the at least one of the phase shifter and attenuator, wherein the voltage source is operable adjust a coupling coefficient of the at least one of the phase shifter and attenuator. In some embodiments, the network of magnetic interconnects forms a uniform geometrical mesh of magnetic interconnects.

[0079] In another example, a system is provided which comprises: a memory; a processor coupled to the memory, the processor having a cellular neural network which comprises an apparatus according to the apparatus described above; and a wireless interface for allowing the processor to couple to another device.

[0080] In another example, a method is provided which comprises: applying an AC voltage to a plurality of oscillators positioned at cross-points of a network of magnetic interconnects; and applying a DC voltage to a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects. In some embodiments, at least one of the oscillators of the plurality of oscillators is a magnetostrictive device. In some embodiments, the magnetostrictive device comprises: a piezoelectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and a non-magnetic layer coupled to the piezoelectric layer. In some embodiments, at least one of the phase shifter and attenuator of the plurality of phase shifters and attenuators comprises: a layer comprising alloys of Co, Fe, Ni, or B; a layer of MgO; and a layer of Ta or Cu.

[0081] In another example, a method is provided comprises: applying a DC current to a plurality of oscillators positioned at cross-points of a network of magnetic interconnects; and applying a DC voltage to a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects. In some embodiments, at least one of the oscillators of the plurality of oscillators is a spin transfer torque (STT) device. In some embodiments, the STT device comprises a magnetic junction. In some embodiments, the magnetic junction is one of a spin valve or a magnetic tunneling junction (MTJ). In some embodiments, the STT device comprises: a dielectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and a fixed magnet coupled to the dielectric layer. In some embodiments, the dielectric layer is MgO.

[0082] In another example, an apparatus is provided which comprises: means for applying an AC voltage to a plurality of oscillators positioned at cross-points of a network of magnetic interconnects; and means for applying a DC voltage to a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects. In some embodiments, at least one of the oscillators of the plurality of oscillators is a magnetostrictive device. In some embodiments, the magnetostrictive device comprises: a piezoelectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and a non-magnetic layer coupled to the piezoelectric layer. In some embodiments, at least one of the phase shifter and attenuator of the plurality of phase shifters and attenuators comprises: a layer comprising alloys of Co, Fe, Ni, or B; a layer of MgO; and a layer of Ta or Cu.

[0083] In another example, a system is provided which comprises: a memory; a processor coupled to the memory, the processor having a cellular neural network which comprises an apparatus according to the apparatus described above; and a wireless interface for allowing the processor to couple to another device.

[0084] In another example, an apparatus is provided which comprises: means for applying a DC current to a plurality of oscillators positioned at cross-points of a network of magnetic interconnects; and means for applying a DC voltage to a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects. In some embodiments, at least one of the oscillators of the plurality of oscillators is a spin transfer torque (STT) device. In some embodiments, the STT device comprises a magnetic junction. In some

embodiments, the magnetic junction is one of a spin valve or a magnetic tunneling junction (MTJ). In some embodiments, the STT device comprises: a dielectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and a fixed magnet coupled to the dielectric layer. In some embodiments, the dielectric layer is MgO.

[0085] In another example, a system is provided which comprises: a memory; a processor coupled to the memory, the processor having a cellular neural network which comprises an apparatus according to the apparatus described above; and a wireless interface for allowing the processor to couple to another device.

[0086] 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 network of magnetic interconnects;

a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects; and

a plurality of oscillators positioned at cross-points of the network of magnetic interconnects.

2. The apparatus of claim 1, wherein at least one of the oscillators of the plurality of oscillators is a magnetostrictive device.

3. The apparatus of claim 2, wherein the magnetostrictive device comprises:

a piezoelectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and

a non-magnetic layer coupled to the piezoelectric layer.

4. The apparatus of claim 3, wherein the piezoelectric layer is formed of one of: lead zirconate titanate (PZT) Pb[ZrxTiiJ0₃; barium titanate (BTO) BaTi0₃; CoFeO, PZT-5, PZT-

4. PZNPT, PMNPT, BiFeCb; Bi₄Ti₃0i2; Polyvinylidene fluoride, or PVDF.

5. The apparatus of claim 3 comprises a voltage source which is to apply an AC voltage to the non-magnetic layer.

6. The apparatus of claim 1, wherein at least one of the oscillators of the plurality of oscillators is a spin transfer torque (STT) device.

7. The apparatus of claim 6, wherein the STT device comprises a magnetic junction.

8. The apparatus of claim 7, wherein the magnetic junction is one of a spin valve or a magnetic tunneling junction (MTJ).

9. The apparatus of claim 6, wherein the STT device comprises: a dielectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and

a fixed magnet coupled to the dielectric layer.

10. The apparatus of claim 9, wherein the dielectric layer is MgO.

11. The apparatus of claim 9 comprises a current source which is to apply a DC current to the fixed magnet.

12. The apparatus of claim 1, wherein at least one of the phase shifter and attenuator of the plurality of phase shifters and attenuators comprises:

a layer comprising alloys of Co, Fe, Ni, or B;

a layer of MgO; and

a layer of Ta or Cu.

13. The apparatus of claim 12 comprises a voltage source coupled to the at least one of the phase shifter and attenuator, wherein the voltage source is operable adjust a coupling coefficient of the at least one of the phase shifter and attenuator.

14. The apparatus of claim 1, wherein the network of magnetic interconnects forms a uniform geometrical mesh of magnetic interconnects.

15. A method comprising:

applying an AC voltage to a plurality of oscillators positioned at cross-points of a network of magnetic interconnects; and

applying a DC voltage to a plurality of phase shifters and attenuators coupled to the network of magnetic interconnects.

16. The method of claim 15, wherein at least one of the oscillators of the plurality of oscillators is a magnetostrictive device.

17. The method of claim 16, wherein the magnetostrictive device comprises:

a piezoelectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and a non-magnetic layer coupled to the piezoelectric layer.

18. The method of claim 15, wherein at least one of the phase shifter and attenuator of the plurality of phase shifters and attenuators comprises:

a layer comprising alloys of Co, Fe, Ni, or B;

a layer of MgO; and

a layer of Ta or Cu.

19. A method comprising:

applying a DC current to a plurality of oscillators positioned at cross-points of a network of magnetic interconnects; and

20. The method of claim 19, wherein at least one of the oscillators of the plurality of oscillators is a spin transfer torque (STT) device.

21. The method of claim 20, wherein the STT device comprises a magnetic junction.

22. The method of claim 21, wherein the magnetic junction is one of a spin valve or a magnetic tunneling junction (MTJ).

23. The method of claim 21, wherein the STT device comprises:

a dielectric layer coupled to a magnetic interconnect of the network of magnetic interconnects; and

a fixed magnet coupled to the dielectric layer.

24. The method of claim 23, wherein the dielectric layer is MgO.

25. A system comprising:

a memory;

a processor coupled to the memory, the processor having a cellular neural network which comprises an apparatus according to any one of apparatus claims 1 to 14; and

a wireless interface for allowing the processor to couple to another device.