Method and apparatus for driving magnetic skyrmions with elastic waves

Abstract

The application provides a method and device for driving a magnetic skyrmion by an elastic wave, the device comprising: a composite film and an elastic wave generating module; the elastic wave generating module is configured to generate an elastic wave, and the elastic wave propagates in the composite film; the number of the composite films in the device is one or more than two; and the number of the elastic wave generating modules is one or more than two. When the device drives the magnetic skyrmion, no current flows through the magnetic film, thereby avoiding the generation of Joule heat on the magnetic film. The technical solution provided by the application has the advantages of fast driving speed of the magnetic skyrmion and greatly improved problems such as large power consumption and easy heating when the magnetic skyrmion is driven.

Description

Technical Field

[0001] This article relates to, but is not limited to, the field of spintronic devices, and in particular to, but is not limited to, methods and apparatus for driving magnetic skyrmions with elastic waves. Background Technology

[0002] Magnetic skyrmions are topologically protected spin structures with quasi-particle properties. They possess advantages such as nanoscale size, high density, and high velocity, and have broad application prospects in magnetic information storage and spintronic devices, attracting widespread attention in recent years. Currently, current-driven methods are the mainstream technology for driving the movement of magnetic skyrmions, but these methods suffer from problems such as high power consumption and heat generation. Summary of the Invention

[0003] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0004] This application provides a method for driving magnetic skyrmions using elastic waves, which achieves high-speed driving of magnetic skyrmions and significantly improves upon the problems of high power consumption and heat generation associated with traditional methods. Existing methods for driving magnetic skyrmions using current require a current density of 10 on the magnetic thin film. 10 A / m 2 Up to 10 11 A / m 2 On the order of magnitude, Joule heating is generated on the magnetic thin film.

[0005] This application provides a device for driving magnetic skyrmions, the device comprising: a composite thin film and an elastic wave generating module;

[0006] The elastic wave generating module is configured such that the elastic wave generated by the elastic wave generating module propagates in the composite film.

[0007] The device contains one or more composite films; the device contains one or more elastic wave generating modules.

[0008] In one embodiment provided in this application, the elastic strain generated by the elastic wave drives the magnetic skyrmion to move through magnetoelastic coupling. The magnetic skyrmion moves in the direction of increasing strain, and the moving speed increases with the strain gradient, thereby realizing the transport of the magnetic skyrmion.

[0009] In one embodiment provided in this application, the wavelength of the elastic wave is 1 μm to 50 μm, and the frequency of the elastic wave is 100 MHz to 5 GHz.

[0010] In one embodiment provided in this application, the composite thin film includes a metal layer and a magnetic thin film layer;

[0011] The magnetic thin film layer has two adjacent upper and lower layers, both of which are metal layers.

[0012] The composite film includes one or more magnetic film layers;

[0013] In one embodiment provided in this application, the metal layer and the magnetic thin film layer in the composite film can be stacked alternately in sequence; alternatively, the repeating units can be stacked in the form of "metal layer-magnetic thin film layer-metal layer".

[0014] The material of the metal layer is selected from any one or more of the metal elements in the sixth period, the metal elements in the eighth group, and the metal elements in the VB group.

[0015] In one embodiment provided in this application, the material of the metal layer is selected from any one or more of Pt, Ir, Ta, W, Ru, Mo, Mn and IrMn.

[0016] In one embodiment provided in this application, the magnetic thin film layer is anisotropic in the vertical direction;

[0017] In one embodiment provided in this application, the magnetic thin film layer has a vertical magnetic anisotropy field of less than 5 mT in the vertical direction.

[0018] In one embodiment provided in this application, the thickness ratio of the magnetic thin film layer to the metal layer is (1 to 30):(1 to 30).

[0019] In one embodiment provided in this application, the material of the magnetic thin film layer is selected from metals of the sixth period and alloys of any one or more elements from Group VIII metals excluding osmium, iridium, and platinum.

[0020] or,

[0021] Metallic elements of the sixth period, alloys of any one or more elements of Group VIII, alloys of Group VIII metallic elements and nonmetallic elements of the second period;

[0022] In one embodiment provided in this application, the material of the magnetic thin film layer is selected from any one or more of Co, CoFeB, FeGe, CoNi, CoGe, CoFeGe, CoFeGd, CoFeNi, and CoZnMn.

[0023] In one embodiment provided in this application, the elastic wave generating module is any one or both of a transverse wave generating module and a longitudinal wave generating module.

[0024] The transverse wave generating module is configured such that the transverse wave generated by the transverse wave generating module propagates within the composite film.

[0025] When the elastic wave passes through the magnetic film in the composite film, it can generate magnetic skyrmions.

[0026] The longitudinal wave generating module is configured such that the longitudinal waves generated by the longitudinal wave generating module propagate within the composite film.

[0027] In one embodiment provided in this application, the elastic wave generating module is a surface acoustic wave generating module, and the surface acoustic wave generating module is configured to propagate the surface acoustic wave generated by the surface acoustic wave generating module within the composite film.

[0028] In one embodiment provided in this application, the surface acoustic wave generating module is an interdigital transducer, and the surface acoustic wave generating module is disposed on a piezoelectric substrate;

[0029] In one embodiment provided in this application, the material of the piezoelectric substrate is selected from any one or more of lithium niobate, lithium tantalate, aluminum nitride, and quartz.

[0030] In one embodiment provided in this application, interdigitated electrodes are fabricated on a piezoelectric substrate to serve as interdigitated transducers, forming a surface acoustic wave delay line. The interdigitated transducers excite surface acoustic waves, and the composite film is disposed along the propagation path of the surface acoustic waves.

[0031] In one embodiment provided in this application, two sets of interdigital transducers, one horizontal and one vertical, are fabricated on a piezoelectric substrate. The periods of each set of interdigital transducers may be equal or different, and the periods may differ by several micrometers. The included angle between the two sets of interdigital transducers, horizontal and vertical, is 0°-90°.

[0032] The period of the interdigital transducer is 1 μm to 50 μm.

[0033] In one embodiment provided in this application, the elastic wave generating module and / or composite film can be disposed between the waveguide layer and the piezoelectric substrate; alternatively, a waveguide layer can be first covered on the piezoelectric substrate, and then the composite film and elastic wave generating module can be disposed on the waveguide layer.

[0034] In one embodiment provided in this application, the thickness of the piezoelectric substrate can be from 0.1 mm to 0.5 mm, and the thickness of the waveguide layer can be from 200 nm to 800 nm (the thickness ratio of the piezoelectric substrate to the waveguide layer can be (1000 to 5000):(2 to 8)); the waveguide layer can be made of silicon dioxide. The interdigital transducer electrode aperture is 200 μm to 2000 μm long, 200 nm to 12 μm wide, and 50 nm to 300 nm thick (or scaled up or down based on this size ratio); the interdigital transducer can be made of metal materials such as Al, Cu, and Pt.

[0035] On the other hand, this application provides the application of the above-described device for driving magnetic skyrmions in transistors, logic gates, spin nano-oscillators, and memories.

[0036] On another aspect, this application provides a method for moving a magnetic skyrmion driven by an elastic wave, using the above-described device for driving the magnetic skyrmion, comprising the following steps: setting the composite thin film along the path of the elastic wave propagation;

[0037] The magnetic skyrmions are generated in the composite film; driven by the elastic wave, the magnetic skyrmions move within the composite film along the propagation direction of the elastic wave.

[0038] In one embodiment provided in this application, the elastic wave is selected from any one or both of transverse waves and longitudinal waves.

[0039] In one embodiment provided in this application, the elastic wave is a surface acoustic wave;

[0040] In one embodiment provided in this application, the surface acoustic wave is any one or more of Rayleigh waves, Love waves, or horizontal shear waves;

[0041] In one embodiment provided in this application, the wavelength of the surface acoustic wave is 2 μm to 50 μm.

[0042] In one embodiment provided in this application, the magnetic skyrmion is a Néel-type magnetic skyrmion or a Bloch-type magnetic skyrmion;

[0043] In one embodiment provided in this application, the size of the magnetic skyrmion is 10 nm to 3 μm;

[0044] In one embodiment provided in this application, the magnetic skyrmion is a magnetic skyrmion generated by the antisymmetric spin exchange effect (Dzyaloshinskii-Moriya interaction (DMI)).

[0045] This application provides a novel method for driving magnetic skyrmions. Compared with existing technologies that use current to drive magnetic skyrmions, this application uses surface acoustic waves (SAWs) to drive magnetic skyrmions at a speed comparable to that of current-driven magnetic skyrmions, and offers the following advantages: the device does not require a continuous application of direct current during operation, reducing power consumption and preventing device overheating. By changing the amplitude and wavelength of the SAWs, the speed and displacement trajectory of the magnetic skyrmions can be adjusted, achieving precise control of the magnetic skyrmions.

[0046] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application may be realized and obtained by means of the methods described in the description. Attached Figure Description

[0047] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0048] Figure 1 This is a schematic diagram of the device structure of a surface wave driven magnetic skyrmion in Embodiment 1 of this application.

[0049] Figure 2 The simulation results of the motion trajectory of the surface wave driven magnetic skyrmion in Example 1 of this application are shown.

[0050] Figure 3 This is a schematic diagram of the surface acoustic wave driven magnetic skyrmion device with a waveguide layer in Embodiment 2 of this application.

[0051] Figure 4 This is a graph showing the relationship between the strain gradient and the wavelength of the surface acoustic wave in Embodiment 1 of this application.

[0052] Figure reference numerals: 1. Piezoelectric substrate; 2. Interdigitated transducer; 3. Heavy metal layer; 4. Magnetic thin film layer; 5. Heavy metal layer; 6. Waveguide layer. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application are described in detail below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be arbitrarily combined with each other.

[0054] Example 1

[0055] This embodiment provides a method for driving a magnetic skyrmion using surface acoustic waves, such as... Figure 1As shown, the structure includes a piezoelectric substrate 1, which is a lithium niobate substrate. Interdigital transducers 2, composed of 100 nm thick aluminum electrodes, are covered on the piezoelectric substrate to form a surface acoustic wave (SAW) delay line structure. Between the two pairs of interdigital transducers, four multilayered stacked films, each consisting of a strip-shaped Pt heavy metal layer 3, a CoFeB magnetic thin film layer 4, and a Ta heavy metal layer 5 (repeated twice with Pt-CoFeB-Ta as the repeating unit), are covered. The Pt layer is 3 nm thick, the CoFeB layer is 1 nm thick, and the Ta layer is 2 nm thick. The composite film is 200 μm long and 50 μm wide. A short-pulse radio frequency signal in the nanosecond to microsecond range is input to the input of the interdigital transducers to excite SAW waves (the wavelength of SAW waves is 2 μm, the frequency is 2.1 GHz, and they are horizontal shear waves). The SAW waves pass through the multilayered stacked films.

[0056] Surface acoustic waves can generate magnetic skyrmions when passing through a magnetic thin film. The magnetic thin film is perpendicularly anisotropic (the perpendicular magnetic anisotropy field of the magnetic thin film layer in the vertical direction is less than 5 mT), and Néel-type magnetic skyrmions with a diameter of about 30 nm are generated by antisymmetric spin exchange interaction (Dzyaloshinskii-Moriya interaction (DMI)).

[0057] Because the magnetic thin film is located in the propagation path of the surface acoustic wave (SAW), when the SAW passes through the magnetic thin film, at the antinodes, the elastic stress induced by the SAW reaches its maximum and the strain reaches its minimum in the multilayered, stacked thin film. At the nodes, the elastic stress induced by the SAW in the magnetic thin film / heavy metal multilayer thin film reaches its minimum and the strain reaches its maximum. The elastic stress and strain generated by the SAW drive the magnetic skyrmions to move through magnetoelastic coupling. The magnetic skyrmions move in the direction of increasing strain, and their moving speed increases with the strain gradient (e.g., ...). Figure 4 As shown, the strain gradient increases as the wavelength of the surface acoustic wave decreases, and the moving speed increases with the strain gradient, thus realizing the transport of magnetic skyrmions.

[0058] Figure 2 The simulation results show the trajectory of a magnetic skyrmion driven by a surface acoustic wave (SAW) with a wavelength of 2 μm. Within 5 ns, the magnetic skyrmion moves forward 100 nm at a speed of 20 m / s. By adjusting the frequency and power of the RF signal input to the interdigital transducer, the wavelength and amplitude of the SAW can be changed, thus controlling and adjusting the magnetic skyrmion's speed and trajectory, achieving effective control of the magnetic skyrmion.

[0059] Example 2

[0060] like Figure 3As shown, the only difference between Example 2 and Example 1 is that a 500nm thick silicon dioxide waveguide layer 6 is covered on the surface of the piezoelectric substrate 1, and the interdigital transducer 2 is disposed between the silicon dioxide waveguide layer 6 and the piezoelectric substrate 1. Multiple layers of repeatedly stacked thin films are disposed on the silicon dioxide waveguide layer 6, and the parameters and positions of the remaining structures are the same as in Example 1.

[0061] A short-pulse radio frequency signal in the nanosecond to microsecond range is input to the input terminal of the interdigital transducer. The excited surface acoustic wave is a Love wave, which is a guided wave (wavelength of 2μm and frequency of 2GHz). The wave particle vibration mode is horizontal shear, and the acoustic wave energy is concentrated in the waveguide layer.

[0062] Surface acoustic waves can generate magnetic skyrmions when passing through a magnetic thin film. The magnetic thin film is perpendicularly anisotropic (the perpendicular magnetic anisotropy field of the magnetic thin film layer in the vertical direction is less than 5 mT), and Néel-type magnetic skyrmions with a diameter of about 30 nm are generated by antisymmetric spin exchange interaction (Dzyaloshinskii-Moriya interaction (DMI)).

[0063] Within 5 ns, the magnetic skyrmion moved forward 126 nm at a speed of 25.2 m / s.

[0064] Comparative Example 1

[0065] Existing technology 1: Observation of room-temperature magnetic skyrmions and their current-driven dynamics in ultrathin metallic ferromagnets. Nature Materials, 2016, 15(5): 501-506. The second paragraph in the left column on page 505 mentions a method of driving magnetic skyrmions with current. The speed of the magnetic skyrmions driven by this method is 30 m / s; the current density flowing through the magnetic thin film is 4.8 × 10⁻⁶ m / s. 11 A / m 2 .

[0066] In Embodiment 1 of this application, the driving magnetic skyrmion does not allow current to flow on the magnetic thin film, thus avoiding Joule heating caused by current on the magnetic thin film.

[0067] It is evident that the technical solution provided in this application drives magnetic skyrmions at high speed, greatly improving the problems of high power consumption and easy heat generation when driving magnetic skyrmions.

[0068] Comparative Example 2

[0069] Existing technology 2: Electrical Generation and Deletion of Magnetic Skyrmion-Bubbles via Vertical Current Injection. Advanced Materials, 2021, 33(45):2104406. Paragraph 0006 mentions a method of voltage-driven magnetic skyrmions, in which the magnetic skyrmions driven by the method have a velocity of about 16 μm / s; the applied voltage is 1 V.

[0070] In the embodiments of this application, the driving magnetic skyrmion does not allow current to flow on the magnetic thin film, thus avoiding the generation of Joule heating caused by current on the magnetic thin film.

[0071] It is evident that the technical solution provided in this application drives magnetic skyrmions at high speed, greatly improving the problems of high power consumption and easy heat generation when driving magnetic skyrmions.

Claims

1. A device for driving magnetic skyrmions, characterized in that, The device includes: a composite thin film and an elastic wave generating module; The elastic wave generating module is configured such that the elastic wave generated by the elastic wave generating module propagates in the composite film. The device contains one or more composite films; the device contains one or more elastic wave generating modules. The composite film includes a metal layer and a magnetic film layer; The magnetic thin film layer has two adjacent upper and lower layers, both of which are metal layers. The composite film includes one or more magnetic film layers; The material of the metal layer is selected from any one or more of the metal elements in the sixth period, the metal elements in group VIII, and the metal elements in group VB. The magnetic thin film layer is made of any one or more alloys of metals from the sixth period and Group VIII metals excluding osmium, iridium, and platinum. or, An alloy composed of one or more elements from the sixth period or group VIII metals and nonmetals from the second period.

2. The apparatus according to claim 1, characterized in that, The material of the metal layer is selected from any one or more of Pt, Ir, Ta, W, Ru, Mo, Mn and IrMn.

3. The apparatus according to claim 2, characterized in that, The material of the magnetic thin film layer is selected from any one or more of Co, CoFeB, FeGe, CoNi, CoGe, CoFeGe, CoFeGd, CoFeNi and CoZnMn.

4. The apparatus according to claim 2 or 3, characterized in that, The magnetic thin film layer is anisotropic in the vertical direction.

5. The apparatus according to claim 4, characterized in that, The magnetic thin film layer has a vertical magnetic anisotropy field of less than 5 mT in the vertical direction.

6. The apparatus according to claim 2 or 3, characterized in that, The thickness ratio of the magnetic thin film layer to the metal layer is (1 to 30):(1 to 30).

7. The apparatus according to any one of claims 1 to 3, characterized in that, The elastic wave generating module is any one or both of the transverse wave generating module and the longitudinal wave generating module. The transverse wave generating module is configured such that the transverse wave generated by the transverse wave generating module propagates within the composite film. The longitudinal wave generating module is configured such that the longitudinal waves generated by the longitudinal wave generating module propagate within the composite film.

8. The apparatus according to claim 7, characterized in that, The elastic wave generating module is a surface acoustic wave generating module, and the surface acoustic wave generating module is configured to propagate the surface acoustic wave generated by the surface acoustic wave generating module within the composite film.

9. The apparatus according to claim 8, characterized in that, The surface acoustic wave generation module is an interdigital transducer.

10. The apparatus according to claim 9, characterized in that, The surface acoustic wave generating module is mounted on a piezoelectric substrate.

11. The apparatus according to claim 10, characterized in that, The piezoelectric substrate is made of any one or more of lithium niobate, lithium tantalate, aluminum nitride, and quartz.

12. The use of the device according to any one of claims 1 to 11 in a transistor, logic gate, spin nanooscillator, or memory.

13. A method for moving a magnetic skyrmion driven by an elastic wave, using the apparatus of any one of claims 1 to 11, comprising the following steps: The composite film is disposed along the path of the elastic wave propagation; The magnetic skyrmions are generated in the composite film; driven by the elastic wave, the magnetic skyrmions move within the composite film along the propagation direction of the elastic wave.

14. The method for moving a magnetic skyrmion driven by an elastic wave according to claim 13, wherein, The elastic wave is selected from any one or both of transverse and longitudinal waves.

15. The method for moving a magnetic skyrmion driven by an elastic wave according to claim 13 or 14, wherein, The elastic wave is a surface acoustic wave.

16. The method for moving a magnetic skyrmion driven by an elastic wave according to claim 15, wherein, The surface acoustic wave is any one or more of Rayleigh waves, Love waves, or horizontal shear waves.

17. The method for driving the movement of a magnetic skyrmion using an elastic wave according to claim 15, wherein, The wavelength of the surface acoustic wave is from 1 μm to 50 μm.

18. The method for moving a magnetic skyrmion driven by an elastic wave according to claim 13 or 14, wherein, The magnetic skyrmion is either a Néel-type magnetic skyrmion or a Bloch-type magnetic skyrmion.

19. The method for moving a magnetic skyrmion driven by an elastic wave according to claim 18, wherein, The size of the magnetic skyrmions ranges from 10 nm to 3 μm.

20. The method for moving a magnetic skyrmion driven by an elastic wave according to claim 18, wherein, The magnetic skyrmions are magnetic skyrmions produced by the antisymmetric spin exchange effect.

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