WO2016193552A1 - Élément de production d'ondes de spin et composant logique comportant un tel élément - Google Patents

Élément de production d'ondes de spin et composant logique comportant un tel élément Download PDF

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Publication number
WO2016193552A1
WO2016193552A1 PCT/FI2016/050402 FI2016050402W WO2016193552A1 WO 2016193552 A1 WO2016193552 A1 WO 2016193552A1 FI 2016050402 W FI2016050402 W FI 2016050402W WO 2016193552 A1 WO2016193552 A1 WO 2016193552A1
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domain wall
ferroelectric
element according
pinned
magnonic
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PCT/FI2016/050402
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English (en)
Inventor
Sebastiaan VAN DIJKEN
Ben VAN DE WIELE
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Aalto University Foundation
Universiteit Gent
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Publication of WO2016193552A1 publication Critical patent/WO2016193552A1/fr

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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
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F10/00—Thin magnetic films, e.g. of one-domain structure
    • H01F10/32—Spin-exchange-coupled multilayers, e.g. nanostructured superlattices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P3/00—Waveguides; Transmission lines of the waveguide type
    • H01P3/16—Dielectric waveguides, i.e. without a longitudinal conductor
    • H01P3/165—Non-radiating dielectric waveguides
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K19/00—Logic circuits, i.e. having at least two inputs acting on one output; Inverting circuits
    • H03K19/02—Logic circuits, i.e. having at least two inputs acting on one output; Inverting circuits using specified components
    • H03K19/16—Logic circuits, i.e. having at least two inputs acting on one output; Inverting circuits using specified components using saturable magnetic devices
    • H03K19/168—Logic circuits, i.e. having at least two inputs acting on one output; Inverting circuits using specified components using saturable magnetic devices using thin-film 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
    • H10N50/20—Spin-polarised current-controlled 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

Definitions

  • the invention relates to magnonic elements, i.e. elements taking advantage of magnetic waves known as spin waves.
  • the invention relates to logic components utilizing such element.
  • the invention can be used in nanoelectronic devices utilized in information and communication technology, for example.
  • ICT information and communication technology
  • semiconductor electronics and progress in optical (photonic) technologies.
  • Severe challenges are, however, foreseen in nanoelectronics when further downscaling (following Moore's law) leads to more and more heat dissipation per unit area. Therefore, ICT demands new materials for post-silicon computing.
  • Novel technologies and complementary logic circuits need to be developed to overtake special-task data processing that challenges
  • SW spin wave
  • Thin film bi-layer structures with polarized ferroelectric and ferromagnetic zones that can be used for producing spin waves are in general discussed in articles by Lahtinen, T. H. E. et al, Electric-field control of magnetic domain wall motion and local magnetization reversal, Sci. Rep. 2, 2012 and Van de Wiele, B. et al, Electric field driven magnetic domain wall motion in ferromagnetic-ferroelectric heterostructures, Applied Physics Letters 104, 2014.
  • the latter one discusses spin wave emissions produced by moving magnetic domain walls at high velocities above a threshold velocity of about 1500 m s, whereby a spin wave emission phenomenon similar to breaking the sound wall for acoustic waves or Cherenkov effect for moving charges takes place.
  • the emission process is not well controllable and it does not occur at a well-defined physical location. Also, no practically feasible implementations suitable for logic circuits, for example, are disclosed.
  • a particular aim is to provide an element, which suits as a building block of a coherent spin wave source, and a logic component comprising such source.
  • the invention is based on oscillating a pinned magnetic domain wall contained in magnetic material using electric oscillatory actuation so as to pump energy to the domain wall. As a result, spin waves are emitted from the domain wall at the frequency of the oscillatory actuation.
  • the invention thus provides a magnonic element for producing spin wave emissions, the element comprising at least one magnetic material zone containing at least one pinned magnetic domain wall capable of oscillating and an electric oscillatory actuator adapted to oscillate the pinned magnetic domain wall at an oscillation frequency for emitting spin waves therefrom at said oscillation frequency.
  • the magnetic domain wall can be pinned in a zone of ferromagnetic material by a magnetic anisotropy boundary.
  • the anisotropy boundary for its part, can be induced by a suitable coupling zone, for example an underlayer structure, underlayer structure onto which the ferromagnetic zone is arranged as a layer, which is optionally patterned as an elongated wire. Detailed embodiments are discussed below.
  • magnonic logic component comprises a first magnonic element according of the kind described above for emitting coherent spin waves, at least one logic element capable of interacting with the spin waves emitted, and a second magnonic element for detecting the spin waves emitted.
  • the invention is defined by what is stated in the independent claims.
  • the invention provides significant advantages.
  • the invention allows for emitting short wavelength spin waves, as the wavelength is dependent on the frequency of oscillation. Electric actuation suits for oscillation at frequencies up to at least 100 GHz, whereby very short wavelength spin waves can be produced.
  • the wavelength can be as short as 1 ⁇ - 15 nm. Particular advantages in this respect are gained when the magnetic domain wall is pinned by a narrow magnetic anisotropy boundary.
  • the wavelength of the spin waves is also easily tunable by the frequency of the actuator.
  • the actuator can provide an AC driving signal, whose frequency, typically 100 MHz - 100 GHz, directly determines the wavelength, wave vector and group velocity of the resulting spin waves.
  • This type of well-defined emission is herein called monochromatic emission.
  • the actuator can use for example an AC current or an AC electric field to couple with the magnetic domain wall.
  • a particularly efficient emitter can be achieved if the oscillatory actuator is adapted to couple an AC electric field to a layer under the pinned domain walls is used for bringing the domain walls into oscillatory motion.
  • the efficiency of the process is particularly high when the actuation takes place at a resonance frequency of the magnetic domain wall.
  • the present element is not restricted to only one spin wave emitting point but can contain two or more pinned magnetic domain walls, which are oscillated using the electric oscillatory actuation simultaneously and in synchronization, which guarantees full coherence of spin waves originating from different physical locations.
  • the element according to the invention can be used as a building block for a new technology platform based on magnonics rather than silicon-based electronics. Of particular importance are implementations where a plurality of magnetic domain walls is induced by the same ferroelectric domain wall -containing underlayer.
  • the dependent claims are directed to selected embodiments of the invention.
  • the at least one magnetic material zone comprises at least one microwire or nanowire in which the pinned magnetic domain wall separates two or more magnetic domains with different magnetization along the length direction of the wire.
  • the magnetic material zone is provided as a wider layer.
  • the oscillatory actuator is adapted to oscillate the pinned magnetic domain wall at a resonance frequency of the pinned magnetic domain wall, whereby the domain walls efficiently absorbs energy for emitting the spin waves.
  • the actuator can be adapted to produce an internal domain wall resonance, such as a local standing spin wave resonance mode, for the oscillating pinned magnetic domain wall.
  • domain wall structures have many different resonance modes over a broad frequency range. In particular in a nanowire geometry, several resonance frequencies exist.
  • the oscillation of the pinned magnetic domain wall takes place in a direction perpendicular to the pinned magnetic domain wall, but other modes of oscillation are possible too.
  • the resonant oscillation perpendicular to the domain wall defines the minimum frequency for spin wave emission.
  • the oscillation frequency of the actuator is tunable for providing a tunable-wavelength spin wave source.
  • the at least one magnetic material zone comprises ferromagnetic material.
  • the coupling zone being capable of inducing the pinned magnetic domain wall in the at least one magnetic material zone.
  • the at least one magnetic material zone can be provided as a first layer of magnetic material and the coupling zone as second layer having an interface with the first layer, whereby the at least one pinned domain wall is created in the first layer through coupling of the first and second layers at the interface region.
  • Induction of the magnetic domain wall through such mechanism results in abrupt change in anisotropy properties of the magnetic material zone and very local pinning of the magnetic domain wall.
  • This further provides particularly advantageous spin wave emission properties as concerns for example monochromaticity and small wavelength.
  • the intrinsic pinning mechanism does not suffer from lithographic limitations and forms a particularly interesting feature of the present technology.
  • the magnetic material zone is arranged as a layer of magnetic material on a substrate or other kind of an underlayer capable of inducing said pinned magnetic domain wall in the at least one magnetic material zone.
  • the underlayer itself may for example comprise at least two domains separated by a domain wall, which is coupled to the magnetic material zone.
  • the underlayer may e.g. induce in the magnetic material zone a magnetic anisotropy boundary onto which the magnetic domain walls are pinned.
  • two magnetic domains with different anisotropy and separated by an anisotropy boundary are formed.
  • a particular example of this kind of an underlayer is a ferroelectric layer with a
  • ferroelectric domain wall separating two ferroelectric domains with different polarizations, each domain inducing a different magnetic anisotropy in ferromagnetic material superimposed on the ferroelectric layer.
  • the ferroelectric domain wall induces a narrow anisotropy boundary on which the induced magnetic domain wall pins. This way, a localized magnetic domain wall over which the magnetization direction changes over a very short distance can be formed. Oscillatory behavior of such magnetic domain wall is also very well defined. Contrary to prior approaches where domain walls are pinned to geometrical constrictions, i.e. notches, this technique accomplishes ferromagnetic domain wall pinning on the nanometer space scale of the ferroelectric domain wall, resulting in sharp well-defined harmonic pinning potentials. In other words, the present kind of spin wave source is localized and not generally defined by lithographic resolution and tolerances, but the small width of the ferroelectric domain wall.
  • an underlayer of the kind described above is only one example of suitable coupling zones. Such layer may be placed also on top of the magnetic material layer, or the zones can reside even laterally, provided that there is a coupling between the zones that can induce a pinned magnetic domain wall in the magnetic material zone.
  • a plurality i.e. at least two magnetic domains walls capable of being oscillated and spin wave emissions are produced simultaneously from at least two magnetic domain walls by oscillating them using electric oscillatory actuation.
  • This can be achieved in various ways.
  • There may for example be a plurality of separate magnetic material zones each containing a magnetic domain wall.
  • several domain walls can also be formed into a single magnetic material zone.
  • the at least one magnetic material zone comprises at least one ferromagnetic nanowire or micro wire crossing at least one domain wall of the underlayer, such as the ferroelectric domain wall mentioned above.
  • a very localized pinned magnetic domain wall is formed.
  • the wires are typically arranged parallel to each other at the location of the underlayer domain wall.
  • the two ferroelectric domains separated by the ferroelectric domain wall are orthogonally in-plane polarized, thereby inducing orthogonally magnetized ferromagnetic domains with orthogonally uniaxial magnetic anisotropy and a pinned ferromagnetic domain wall in the ferromagnetic material crossing the domain wall.
  • Other types of induced anisotropy are equally possible, e.g. when there are two ferroelectric domains in the underlayer, one having in-plane polarization and the other having out-of- plane polarization.
  • the actuator is adapted to apply an alternating electric field through the ferroelectric layer for oscillating the magnetic domain wall (or walls) pinned on the ferroelectric layer.
  • the actuator is adapted to feed alternating current, in particular spin-polarized current, through the magnetic material zone (or zones) and the pinned magnetic domain wall (or walls) contained in them. Both mechanisms result in that the pinned magnetic domain wall (or walls) start to oscillate, whereby energy is pumped thereto for emitting the spin waves.
  • the electric actuation is adapted to oscillate all or at least some of the domain walls simultaneously.
  • coherent spin waves are emitted by the domain walls.
  • Practical applications do not require the spin waves emitted being necessarily in the same phase, although they can be.
  • oscillatory actuation of the domain walls may take place in the same phase or with a known phase difference.
  • the two or more pinned magnetic domain walls are induced by a single ferroelectric domain wall, which the magnetic material zone crosses or several different magnetic material zones cross.
  • at least some of the pinned magnetic domain walls can be situated in different magnetic material zones preferably arranged parallel to each other. This is the case for example with two parallel ferromagnetic nanowires crossing a single ferroelectric domain wall.
  • a magnetic domain wall is disclosed that is strongly pinned to a ferroelectric domain wall.
  • the magnetic domain wall can be excited by either an AC electric current or an AC electric field. The excitation can result in a back- and- forth motion of the domain wall, typically over a distance of only a few nanometer, for example a distance of about 0.1 to 50 nm, for example 1 to 10 nm.
  • the domain wall remains highly localized. The velocity of the domain wall is non-constant during this motion. It continuously oscillates.
  • excitation of the domain wall with an AC electric current or an AC electric field induces
  • the frequency of the spin waves is identical to the AC driving frequency.
  • FIG. 1A shows a cross-sectional side view of a layer structure according to one
  • Figs. IB and 1C show planar views of the layers of Fig. 1A.
  • Fig. ID illustrates the behavior of magnetization at the location of the magnetic domain wall in a structure according to Figs. 1A-1C.
  • Figs. 2A and 2B show oscillatory electric actuators coupled to the structure of Fig. 1A according to embodiments of the invention.
  • Figs. 3A and 3B show a top view and perspective view, respectively, of two potential structures and oscillatory actuators of coherent spin wave emitting elements according to embodiments of the invention.
  • Figs. 4A and 4B show a cross-sectional end view and top view, respectively, of an element with two magnetic domain walls pinned by a single underlay er domain wall.
  • Figs. 5A and 5B show a cross-sectional end view and top view, respectively, of an element with two magnetic domain walls pinned by separate underlayer domain walls.
  • Fig. 6 schematically illustrates a logic component utilizing a spin wave emitting element according to the invention.
  • domain refers to a region of material in which a particular property of interest
  • domain wall [like in “(ferro)magnetic domain wall” or “ferroelectric domain wall”] is an interface between two different domains, where the property of interest (magnetization or electric polarization, respectively) makes a transition (change of orientation) from one state to another.
  • a zone of material [like “(ferro)magnetic material zone” or “ferroelectric material zone”] can in general contain one or more domains and domain walls. Width of a domain wall is defined as the distance over which the transition essentially takes place.
  • ferromagnetic is used in broad sense covering also materials known as ferrimagnetic.
  • Anisotropy boundary refers to a region, where the symmetry, direction and/or strength of the anisotropy of the material changes locally.
  • an anisotropy boundary as herein used, is capable of pinning a ferromagnetic domain wall intersecting or located close to the anisotropy boundary.
  • Coupling zone refers to a zone of material close to the magnetic material zone capable of inducing the pinned magnetic domain wall in the magnetic material zone through physical coupling of the zones.
  • Examples of coupling zones include a layer of ferroelectric or antiferromagnetic multiferroic material with a domain wall provided therein. Such layers couple with ferromagnetic material generating the desired pinned ferromagnetic domain wall.
  • Oscillation of a magnetic domain wall can mean oscillation of its location with respect to its resting location, i.e. location without the actuation. In typical embodiments, the oscillation takes place in a direction perpendicular to the domain wall, for example back and forth along a ferromagnetic (micro or nano)wire containing a magnetic domain wall.
  • the domain wall can be transverse to the direction of the wire or have another orientation. Additionally Oscillation' can also refer to oscillation modes of the magnetization, inside the magnetic domain wall. In typical embodiments, these oscillation modes are standing spin waves localized in the domain wall, e.g. along the direction of the anisotropy boundary. "Coherent" spin waves mean spin waves that have fixed phase relation, i.e, either the same phase or a constant non-zero phase difference.
  • “Nanowire” is an elongated formation of material whose transverse dimensions are less than 1 ⁇ , in particular 100 nm or less.
  • “Microwire” is an elongated formation of material whose transverse dimensions are 1 ⁇ - 1 mm.
  • a magnetic domain wall is disclosed that is strongly pinned to a ferroelectric domain wall.
  • the magnetic domain wall is excited and excitation can result in a back-and- forth motion of the domain wall, typically over a distance of only a few nanometer.
  • the domain wall remains highly localized.
  • the velocity of the domain wall is non-constant during this motion.
  • the terms “moving” and “exciting” basically refer to the same phenomenon, and the term “moving” is to be understood as covering also the action of “exciting” the wall.
  • Figs. 1 A-C show a structure with a ferroelectric layer 1 1 comprising a first ferroelectric domain 11 A and a second ferroelectric domain 1 IB, whose polarizations are different.
  • the domains 11 A, 1 IB are separated by a ferroelectric domain wall 12, which is perpendicular to the plane of the layer.
  • On top of the ferroelectric layer 11 there is provided a ferromagnetic layer 15.
  • a magnetic domain wall 17 is pinned by this anisotropy boundary 16, defining two magnetic domains 15 A, 15B and acts as a spin wave 10 emitting feature, when brought into oscillation.
  • the domain wall 12 of the ferroelectric layer 11 is "imprinted" to the ferromagnetic layer 15.
  • the parallel alignment between in-plane polarization direction 18A,18B and the in-plane magnetization direction 19A,19B can be different depending on the magnetostriction constant of the ferromagnetic layer (in case of strain transfer) and/or applied magnetic field.
  • the angle difference is 90 degrees, which ensures strong induction of the magnetic domain wall 17.
  • the angle difference takes place in the plane of the layer 11, but can also contain an out-of-plane component or be entirely out-of plane.
  • the polarizations in the two ferroelectric domains need to be different, but many different configurations depending on the type of domain structure and ferroelectric phase and/or material are possible.
  • the polarization in the ferroelectric domains 11A, 1 IB elongates the structural units of the layer.
  • the associated strain induces a uniaxial anisotropy in the ferromagnetic layer, defining there the two ferromagnetic domains 15 A, 15B.
  • ferroelectric domain structure is fully imprinted in the ferromagnetic layer and the ferromagnetic domain wall 16 is also strongly pinned.
  • the ferroelectric layer 11 determines the static equilibrium magnetization state in the ferromagnetic layer 15: while in the ferromagnetic domains 15 A, 15B the magnetization direction is determined by a competition between the uniaxial anisotropy directions and strengths on the one hand and geometry- induced easy magnetization directions (known as shape anisotropy) on the other hand.
  • shape anisotropy geometry- induced easy magnetization directions
  • the oscillating pinned magnetic domain wall required for emission of spin waves can also be created even without a ferroelectric layer as the underlayer.
  • Coupling between the underlayer and the ferromagnetic layer can be mediated via strain as described above by way of example, but other coupling mechanisms are also possible. Variations include in particular exchange bias, local ion migration and charge accumulation, which are all covered by the term "induce”. Some specific examples are described later in this document.
  • the ferroelectric domain wall 12 in the ferroelectric layer 11 and thus the anisotropy boundary 16 pinning the magnetic domain wall 17 in the ferromagnetic layer 15 are very narrow. This extreme lateral confinement enables the emission of short wavelength spin waves.
  • the magnetic domain wall 17 is typically broader than the ferroelectric domain wall 12 and the anisotropy boundary 16, as illustrated in the figures.
  • the width of the pinned magnetic domain wall 17 may range from only few nanometers to at most 1000 nm, such as 5 - 500 nm.
  • Fig. ID illustrates how the direction of magnetization changes uniaxially over this small width by 90 degrees in an exemplary infinite film geometry. With different configurations of the underlayer and overall element geometry or in the presence of an external magnetic field, the magnetization map can be also different.
  • the ferromagnetic layer 15 is narrow also in the transverse lateral direction, i.e. the lateral direction parallel to the direction of the domain wall 17.
  • the layers may be provided in the form of microwires (width 1 - 1000 ⁇ ) or nano wires (width less than 1000 nm).
  • the ferromagnetic material may comprise e.g. Co, Fe, Ni or an alloy containing one or more of these materials.
  • suitable materials is CoFe.
  • the ferroelectric material may comprise e.g. BaTi0 3 , PbTi0 3 , LiTa0 3 , lead zirconium titanate (PZT), triglycerine sulfate (TGS), or polyvinylidene fluoride (PVDF).
  • Fig. 2A shows one possibility for actuating the oscillation of the magnetic domain wall 17, i.e. injecting an alternating current I ac through the ferromagnetic material layer 15 using a current controlling unit 20.
  • the alternating current I ac may be spin-polarized.
  • the current flows perpendicular to the domain wall 17.
  • This causes the magnetic domain wall 16 to oscillate in the pinning potential of the anisotropy boundary. Above a critical frequency, this leads to the emission of spin waves 22 at the frequency of the ac driving current. In a film geometry this spin wave emission can originate in the oscillatory back-and- forth motion of the domain wall done at the same frequency of the excitation.
  • each excitation cycle the potential energy difference between extreme and zero domain wall displacement (in the x-direction of Fig. 2) is dissipated by the oscillator by emitting spin waves and internal damping.
  • confinement effects allow additional domain wall oscillations corresponding to the existence of standing spin wave modes localized inside the domain walls and beating at the excitation frequency.
  • the potential energy stored in the standing spin waves is dissipated by the emitting spin waves and internal damping. In both cases, the wavelength of the emitted spin waves 22 decreases with increasing frequency, providing a high degree of tunability.
  • the oscillation of the domain wall 17 due to the injected current I ac may take place via the spin transfer torque effect, spin Hall effect or Rashba effect, to mention some examples.
  • the actuator may be based on the use of an AC electric field applied to the ferroelectric layer 11 using a voltage controlling unit 23. This field causes the ferroelectric domain wall 12 in the ferroelectric layer 11 to oscillate.
  • the oscillatory motion of the ferroelectric domain wall 12 is mimicked by the anisotropy boundary 16 in the ferromagnetic layer 15.
  • the oscillations of the anisotropy boundary 16 induce oscillations of the ferromagnetic domain wall 17 in the ferromagnetic layer 11 at the same frequency. Again, above a critical frequency this leads to the emission of spin waves 22 at the frequency of the AC electric field. Similarly, the wavelength of the emitted spin waves decreases with increasing frequency, whereby also this actuation scheme offers high degree of tunability. Since the electric current flowing through the device is much reduced in this realization, because ferroelectric layers are insulating, spin wave emission at lower energy consumption levels can be obtained.
  • an alternating voltage can be along many directions, depending on the polarization configuration in the ferroelectric layer.
  • the illustration indicates the application of an alternating voltage along the out-of-plane direction.
  • the voltage may be along the in-plane direction or any other direction too.
  • the inventive spin wave emission mechanism is briefly explained below.
  • Each excitation cycle the potential energy difference between extreme and zero domain wall displacement or between maximum and zero amplitude of internal domain wall standing spin wave profiles is dissipated by the oscillator by emitting spin waves and internal damping.
  • the generated spin waves generally propagate perpendicular to the domain wall, i.e. with a wave front parallel to the domain wall.
  • the ferromagnetic layer 15 acts as a spin wave waveguide.
  • the ferromagnetic domain wall is preferably oscillated at its resonance frequency, whereby actuation energy is efficiently absorbed and dissipated by the domain wall oscillator by emitting large-amplitude spin waves into the nanowire.
  • a nanowire-shaped domain wall oscillator has a plurality of possible resonance modes that can be used, in particular between 1 and 100 GHz.
  • a huge number of internal domain wall resonances exists. The frequency step between these resonances decreases rapidly at higher frequencies leading to an excitation efficiency that only moderately depends on the frequency.
  • Figs 3A and 3B illustrate coherent spin wave emitters containing two spin wave sources and the two different actuation mechanism discussed above applied to them. Both variations comprise similar layer structures having a ferroelectric layer with two domains 31 A, 3 IB; 41 A, 41B like those discussed above with reference to Figs. 1 and 2. Instead of only one ferromagnetic layer, there are provided two separate layers 35, 37; 45, 47 which are parallel to each other and cross the ferroelectric domain wall 32; 42 between the ferroelectric domains 31 A, 3 IB; 41 A, 41B perpendicularly. The layers 35, 37; 45, 47 are preferably arranged as parallel nanowires.
  • both parallel nanowires the magnetization distribution is fixed by the strong anisotropy induced by the ferroelectric layer.
  • Both layers act as ferromagnetic spin wave waveguides into which identical domain walls are induced by the ferroelectric domain wall underneath them by the mechanism discussed above. To be noted is that the spin waves are generated by domain wall oscillators pinned to the same ferroelectric domain wall.
  • Fig. 3A illustrates an actuation mechanism where an AC electrical current (I ac ) fed from a current controller 33 through the waveguides 35, 37 makes, via the spin-transfer-torque effect, the respective domain walls oscillate while emitting spin waves with identical frequency.
  • Identical waveguide dimensions and electrical currents guarantee full coherence between the spin wave sources. It is, however an advantage of this actuation mechanism that a phase difference in the actuation currents directed to each waveguide 35, 37 can be provided, resulting in an identical phase difference between the spin waves.
  • Fig. 3B illustrates an actuation mechanism where an AC electrical field applied on the ferroelectric layer 41A, 41B from an AC voltage (V ac ) controller 43 makes the anisotropy boundary together with the ferromagnetic domain walls of the waveguides 45, 47 oscillate.
  • V ac AC voltage
  • spin waves are emitted at the same frequency and identical waveguide dimensions guarantee full coherence between the spin wave sources.
  • This embodiment has the advantage of being energy- efficient, as the ferroelectric layer is generally insulating and therefore losses are low.
  • the current controller 20, 33 or voltage controller 23, 43 can be adapted to provide a fixed- frequency driving signal for providing a fixed-wavelength spin wave source or comprise means for tuning the frequency of the driving signal for achieving a wavelength-tunable spin wave source.
  • Figs. 4A, 4B, 5A and 5B illustrate two more detailed examples on how to create multiple spin wave emitters allowing for coherent spin wave emission.
  • the example of Figs. 4A and 4B comprises two ferromagnetic nanowires 35A, 35B; 37A, 37B are patterned on top of a ferroelectric layer 31 A, 3 IB with a ferroelectric domain wall 32.
  • a ferromagnetic domain wall 36, 38 is pinned on top of the ferroelectric domain wall 32 in each of the
  • the ferromagnetic nanowires 35A, 35B; 37A, 37B via coupling between the ferroelectric layer and the ferromagnetic nanowires as described before.
  • the ferromagnetic domain walls can be brought into oscillatory motion using an alternating current or an alternating voltage, as also presented above, leading to the emission of spin waves in the ferromagnetic nanowires 35 A, 35B; 37A, 37B.
  • the phase between the spin waves in the two nanowires 35A, 35B; 37A, 37B can be tuned by controlling the phase of electric current in ferromagnetic nanowire 35A, 35B and 37A, 37B.
  • the schematic shows the ferroelectric layer in film geometry. It is also possible to pattern both the ferromagnetic layer and the ferroelectric layer in a nanowire geometry or some other geometry.
  • two ferromagnetic domain walls 77A, 77B in a ferromagnetic nanowire 75A, 75B, 75C are pinned on top of two ferroelectric domain walls 62A, 62B in a ferroelectric layer 61 A, 6 IB, 61C via the previously described coupling mechanism.
  • the ferromagnetic domain walls 77A, 77B can be brought into oscillatory motion using an alternating current or an alternating voltage, as in the previous examples, leading to the emission of spin waves in the ferromagnetic nanowire 75 A, 75B, 75 C.
  • the ferromagnetic layer could for example be a continuous film in the case of electric-field actuation or both the
  • ferromagnetic layer and the ferroelectric layer could be patterned into a nanowire geometry or some other geometry.
  • the number of ferromagnetic domain walls is two.
  • the concepts of Fig. 4A, 4B and 5 A, 5B can be extended to oscillating ferromagnetic domain wall spin wave emitters with more than two domain walls as the spin wave emission points by utilizing more than two parallel nanowires crossing a single ferroelectric domain wall and/or more than two ferroelectric domain walls which a single ferromagnetic wire crosses.
  • the number of domain walls in such variations can be for example 3 - 10.
  • the concepts shown in Figs. 4A, 4B and 5A, 5B can also be combined. That is, there may be both a plurality of ferromagnetic nanowires and a plurality of magnetic domain wall inducing ferroelectric domain walls underneath them.
  • spin waves in parallel nanowires with domain wall oscillators pinned to the same ferroelectric domain wall have identical dispersion properties.
  • the domain wall oscillators emit monochromatic coherent spin waves in all wires.
  • a fixed phase relation between the spin waves in different nanowires can be introduced by tuning the phase of the individual excitation currents (using the configuration of Fig. 3A).
  • anisotropy boundaries and thus pinned magnetic domain walls, capable of emitting spin waves can be formed in other ways. Some of them are briefly discussed below.
  • the ferroelectric layer is replaced by an
  • antiferromagnetic ferroelectric (multiferroic) layer whereby an exchange bias between the antiferromagnetic multiferroic layer and the ferromagnetic layer forms the required anisotropy boundary.
  • the ferromagnetic layer is grown onto another pre-patterned substrate capable of inducing the anisotropy boundary.
  • local ion implantation or proton irradiation is applied to the ferromagnetic layer, using an implantation or irradiation scheme capable of providing an anisotropy boundary in the ferromagnetic layer.
  • the AC current injection actuation scheme illustrated in Figs. 2A and 3A and discussed above in more detail is applicable also to all these alternative structures.
  • the AC field actuation scheme illustrated in Figs. 2B and 3B and discussed above in more detail is applicable to the alternative structure containing the antiferromagnetic ferroelectric (multiferroic) layer underneath the ferromagnetic layer. Multiferroic materials are also insulating by nature, whereby low energy consumption levels are achievable by the AC field actuation.
  • dispersion band gaps for example, can be provided without intervening in the nanowire geometry, again alleviating lithographic restrictions.
  • Fig. 6 shows a schematic example of a logic component 600 utilizing a spin wave source element 610 capable of emitting two coherent spin waves 690 A, 690B upon electrical actuation initiated via a driving signal input 620.
  • the component 600 comprises, two logic inputs 640A, 640B connected to logic elements 630A, 630B capable of interacting with the spin waves 690A, 690B, respectively.
  • the spin wave(s) passing the logic elements are detected at a detector element 670 for providing an output signal at an output 680 of the component 600.
  • the source element 610 can be for example a coherent double-nanowire source as discussed above with reference to Fig. 3A, 3B, 4A or 4B or any variation thereof.
  • the logic elements 630A, 630B can be functionally connected to the nanowire waveguides so as to provide a desired output of the logic component depending on signals provided at the logic inputs.
  • the logic component may utilize the Mach-Zehnder principle. Using this principle, a logic gate performing an AND, NAND, OR, XOR or XNOR operation, for example, can be implemented. By suitable modification, but using the same principle, a magnonic transistor with magnonic source, gate and drain terminals can be implemented.
  • a magnonic element for producing spin wave emissions, comprising at least one magnetic material zone containing at least one pinned magnetic domain wall, and an actuator for exciting or moving the at least one pinned magnetic domain wall, the actuator comprising an electric actuator adapted to oscillate the at least one pinned magnetic domain wall at an oscillation frequency for emitting spin waves having a frequency corresponding to said oscillation frequency.
  • a magnonic logic component of the present technology comprises a first magnonic element for emitting spin waves, at least one logic element capable of interacting with the spin waves emitted, and a second magnonic element for detecting the spin waves emitted by the first magnonic element, wherein first magnonic element is an element of the above kind.
  • the present nanoelectronic devices can be utilized in information and communication technology.
  • the present element in particular when containing two or more coherent spin wave emitting spots, can be used as a spin wave emitting element in a magnonic transistor, a magnonic logic gate, such as a gate performing an AND, NAND, OR, XOR or XNOR operation, a magnonic memory device or magnonic crystal.
  • a magnonic logic gate such as a gate performing an AND, NAND, OR, XOR or XNOR operation
  • magnonic memory device or magnonic crystal magnonic crystal.

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Abstract

La présente invention porte sur un élément à magnon de production d'émissions d'ondes de spin qui comprend une zone de matière ferromagnétique (15) contenant au moins une paroi de domaine magnétique à tige (16) et un actionneur électrique, par exemple fournissant un courant d'attaque en courant alternatif (CA), conçu pour faire osciller la paroi de domaine magnétique à tige à une fréquence d'oscillation permettant d'émettre des ondes de spin ayant une fréquence correspondant à ladite fréquence d'oscillation. De préférence, adjacente à la zone de matière ferromagnétique, une zone de couplage ferroélectrique (11) est agencée de manière à induire ladite paroi de domaine magnétique à tige et permettre une excitation de tension en CA. L'élément peut être utilisé en tant qu'élément d'émission d'ondes de spin dans un composant logique à magnon.
PCT/FI2016/050402 2015-06-05 2016-06-06 Élément de production d'ondes de spin et composant logique comportant un tel élément WO2016193552A1 (fr)

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US10033078B2 (en) * 2016-05-24 2018-07-24 Imec Vzw Tunable magnonic crystal device and filtering method
RU2694020C1 (ru) * 2018-07-27 2019-07-08 Федеральное государственное бюджетное учреждение науки Институт радиотехники и электроники им. В.А. Котельникова Российской академии наук Логический элемент инвертор-повторитель на магнитостатических волнах
JP2022515986A (ja) * 2018-08-01 2022-02-24 ドレクセル ユニバーシティ 固体の同調可能なイオン発振器誘電材料および共振装置

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10033078B2 (en) * 2016-05-24 2018-07-24 Imec Vzw Tunable magnonic crystal device and filtering method
RU2694020C1 (ru) * 2018-07-27 2019-07-08 Федеральное государственное бюджетное учреждение науки Институт радиотехники и электроники им. В.А. Котельникова Российской академии наук Логический элемент инвертор-повторитель на магнитостатических волнах
JP2022515986A (ja) * 2018-08-01 2022-02-24 ドレクセル ユニバーシティ 固体の同調可能なイオン発振器誘電材料および共振装置

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