THz magneton generator based on high-speed movement of antiferromagnetic domain wall

Abstract

The invention provides a THz magneton generator based on high-speed movement of an antiferromagnetic domain wall. The THz magneton generator comprises a heavy metal layer; the antiferromagnetic layer is located on the heavy metal layer, and the magnetic anisotropy of the left half area and the magnetic anisotropy of the right half area of the antiferromagnetic layer are different; current is applied to the heavy metal layer, and spin-orbit torque is generated; the spin-orbit torque drives a Neel wall in the antiferromagnetic layer to move from an area with high magnetic anisotropy to an area with low magnetic anisotropy; when a domain wall in the antiferromagnetic layer passes through the joint of the left half area and the right half area, the equivalent potential energy of the magnetic anisotropy is converted into kinetic energy, the domain wall is driven to move at the speed close to the saturation speed, the domain wall is subjected to Lorentz contraction, and spin waves in the THz frequency band are emitted. The THz magneton generator is low in current density, small in power consumption and high in frequency, the spin wave frequency can be dynamically regulated and controlled through multiple means, and the THz magneton generator is compatible with the semiconductor technology.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductors and spintronic devices, and in particular to a THz (terahertz) magnon generator based on high-speed motion of antiferromagnetic domain walls. Background Art

[0002] Magnonic spin devices transmit and process information by manipulating magnons rather than electrical charges. They offer significant advantages such as zero joule heating and ultra-high speed, enabling ultra-low power consumption and ultra-high frequency response, providing the physical foundation for ultra-low power magnetic sensors and ultra-high frequency chips. Furthermore, the wave properties of magnons, as quasiparticles, enable quantum information transmission, breaking through the physical limitations of traditional semiconductor devices. The research and industrialization of magnon spin devices will drive the upgrading of the new magnetic material industry chain, opening up a new paradigm for "non-von" magnon chips and novel information processing architectures. This will drive the evolution of artificial intelligence, intelligent sensing, information storage, and computing, from devices to products, and open up a new frontier for the AI ​​technological revolution.

[0003] One of the key technologies in magnon spin devices is the generation of magnons. Currently, the main methods for generating magnons include thermal gradients, lasers, coplanar waveguides (microwave magnetic fields), electric currents, and the interaction of spin-orbit moments with micromagnetic structures. The latter three methods are primarily used to excite spin waves at GHz (gigahertz) or lower frequencies, while the fifth method can achieve higher-frequency magnon excitation at ultra-high current densities. The first two methods can be used to excite magnons up to the THz band, but they are difficult to integrate and cannot dynamically control the magnon frequency. The laser equipment required for the laser method is expensive and complex, and the uneven distribution of laser energy in the material can cause local overheating or even damage. The thermal gradient method cannot generate spin waves of a single frequency. Summary of the Invention

[0004] In order to solve the above-mentioned defects in the prior art, the present invention provides a THz magnon generator based on the high-speed motion of antiferromagnetic domain walls.

[0005] The present invention provides a THz magneton generator based on high-speed motion of antiferromagnetic domain walls, comprising:

[0006] Heavy metal layer;

[0007] an antiferromagnetic layer, the antiferromagnetic layer being located on the heavy metal layer, wherein the magnetic anisotropy of the left half region and the right half region of the antiferromagnetic layer are different in magnitude;

[0008] A current is applied to the heavy metal layer to generate a spin-orbit torque; the spin-orbit torque drives the Neely wall in the antiferromagnetic layer to move from a region with high magnetic anisotropy to a region with low magnetic anisotropy; when the domain wall in the antiferromagnetic layer passes through the junction of the left half region and the right half region, the equivalent potential energy of the magnetic anisotropy is converted into kinetic energy, driving the domain wall to move at a speed close to the saturation velocity, causing the domain wall to undergo Lorentz contraction and emit spin waves in the THz frequency band.

[0009] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, the difference between the magnetic anisotropy of the left half region and the right half region is the optimal difference, so that the critical current density of the magnons emitted by the domain walls is minimized.

[0010] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, the step of obtaining the optimal difference comprises:

[0011] Obtaining a relationship curve between the difference and the critical current density of the domain wall emitting magnons through simulation;

[0012] The difference corresponding to the minimum critical current density in the relationship curve is used as the optimal difference.

[0013] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, in the simulation, the magnetic anisotropy of the region with low magnetic anisotropy remains unchanged, and the magnetic anisotropy of the region with high magnetic anisotropy gradually increases. The difference is calculated each time the magnetic anisotropy increases, and the current is gradually increased until the domain wall emits magnons, and the critical current density is calculated based on the increased current.

[0014] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, the frequency of magnons emitted by the domain walls is controlled by regulating the difference between the magnetic anisotropy of the left half region and the right half region, or the magnitude of the current.

[0015] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, the frequency control step of the magnons emitted by the domain walls includes:

[0016] Under the condition that the magnitude of the current remains unchanged, obtaining a relationship curve between the frequency of the domain wall emitting magnetons and the difference through simulation;

[0017] According to the relationship curve, obtaining a difference corresponding to a target frequency of the domain wall emitting magnetons;

[0018] The difference between the magnetic anisotropy of the left half region and the right half region is adjusted to be a difference corresponding to the target frequency, so that the frequency of the domain wall emitting magnetic particles is the target frequency.

[0019] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, the frequency control step of the magnons emitted by the domain walls includes:

[0020] Under the condition that the difference remains unchanged, obtaining a relationship curve between the frequency of the domain wall emitting magnetons and the current density of the current through simulation;

[0021] According to the relationship curve, a current density corresponding to a target frequency of the domain wall emitting magnetons is obtained;

[0022] The magnitude of the current is regulated so that the current density of the current is the current density corresponding to the target frequency, so that the frequency of the domain wall emitting magnetons is the target frequency.

[0023] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, the material used for the heavy metal layer is Pt, and the material used for the antiferromagnetic layer is NiO or α-Fe2O3.

[0024] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, the different magnitudes of magnetic anisotropy between the left and right half regions are achieved through interface design, process control or voltage-controlled magnetic anisotropy effect.

[0025] According to a THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention, the magnetic anisotropy of the left half region is greater than the magnetic anisotropy of the right half region.

[0026] The present invention provides a THz magnon generator based on the high-speed motion of antiferromagnetic domain walls. The invention realizes a stepped magnetic anisotropy structure design by arranging an antiferromagnetic layer on a heavy metal layer, wherein the magnetic anisotropy of the left half region and the right half region of the antiferromagnetic layer are different in magnitude. The spin-orbit torque generated by the current in the heavy metal layer is used to drive the antiferromagnetic Neely wall to move from a high magnetic anisotropy region to a low magnetic anisotropy region. At the step, the equivalent potential energy is converted into kinetic energy, and the domain wall is driven to move at a speed close to the saturation speed under low current density. The domain wall undergoes Lorentz contraction, and spin waves in the THz frequency band are generated. The invention not only has low current density, low power consumption and high frequency, but also the spin wave frequency can be dynamically controlled by various means, is compatible with semiconductor processes, and provides a reliable and efficient new approach for the realization of high-frequency THz magnon generators. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 Schematic diagram of the structure of the THz magnon generator based on high-speed motion of antiferromagnetic domain walls provided by the present invention;

[0029] Figure 2 (a) is the curve of the change of domain wall position over time under current driving, (b) is the oscillation curve of the x component of the Née vector at a specific position in the magnetic domain area over time, (c) is the relationship between the change of the x component of the Née vector and the position, and (d) is the fast Fourier transform result corresponding to (b);

[0030] Figure 3 (a) is the curve of the critical current density of high-frequency magnons emitted by the domain wall as a function of the difference ΔK, and (b) is the curve of the magnon frequency as a function of the difference in magnetic anisotropy between the left and right sides.

[0031] Figure 4 This is a schematic diagram of the relationship between the magnon emission frequency and the current density of the THz magnon generator based on the high-speed motion of the antiferromagnetic domain wall provided by the present invention when K1 = 0.44 meV and K2 = 0.04 meV. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0033] The following combination Figure 1 The present invention describes a THz magnon generator based on high-speed motion of antiferromagnetic domain walls, comprising:

[0034] Heavy metal layer;

[0035] an antiferromagnetic layer, the antiferromagnetic layer being located on the heavy metal layer, wherein the magnetic anisotropy of the left half region and the right half region of the antiferromagnetic layer are different in magnitude;

[0036] A current is applied to the heavy metal layer to generate a spin-orbit torque; the spin-orbit torque drives the Neely wall in the antiferromagnetic layer to move from a region with high magnetic anisotropy to a region with low magnetic anisotropy; when the domain wall in the antiferromagnetic layer passes through the junction of the left half region and the right half region, the equivalent potential energy of the magnetic anisotropy is converted into kinetic energy, driving the domain wall to move at a speed close to the saturation velocity, causing the domain wall to undergo Lorentz contraction and emit spin waves in the THz frequency band.

[0037] The core of the present invention lies in the innovative design of the device structure, such as Figure 1 As shown in the figure, the THz magnon generator based on the high-speed motion of antiferromagnetic domain walls includes a bottom heavy metal layer (HM) and an upper antiferromagnetic layer (AFM).

[0038] The magnetic anisotropy of the left half of the antiferromagnetic layer is different from that of the right half. For example, the magnetic anisotropy K1 of the left half is greater than the magnetic anisotropy K of the right half. 2, , that is, the left half area is a high magnetic anisotropy area, and the right half area is a low magnetic anisotropy area. Or the magnetic anisotropy K1 of the left half area is smaller than the magnetic anisotropy K of the right half area. 2, , that is, the left half area is the low magnetic anisotropy area, and the right half area is the high magnetic anisotropy area.

[0039] When a current J is applied to the heavy metal layer, the generated spin orbit torque (SOT) drives the antiferromagnetic Neel wall from the high magnetic anisotropy region to the low magnetic anisotropy region. Figure 2 As shown in Figure (a), when the domain wall passes through the step (ΔK = |K1 - K2|), the equivalent potential energy (magnetic anisotropy) is converted into kinetic energy, and the movement speed of the domain wall increases rapidly, approaching the saturation speed (spin wave group velocity). The domain wall undergoes Lorentz contraction and emits spin waves in the THz (terahertz) frequency band, as shown in Figure 5. Figure 2 As shown in Figures (b), (c) and (d).

[0040] Figure 2 Figure (a) shows the curve of the change of domain wall position over time under current drive. It can be seen that the speed of the domain wall increases greatly when passing through the magnetic anisotropy step; Figure (b) shows the oscillation change curve of the Née vector x component at a specific position in the magnetic domain area over time; Figure (c) shows the relationship between the change of the Née vector x component and position, indicating that the magnon is excited; Figure (d) corresponds to the Fast Fourier Transform (FFT) result of Figure (b), where the low frequency is the precession frequency caused by SOT, the low-frequency peak is the Née vector precession caused by SOT, and the high frequency is the frequency of the excited magnon.

[0041] In this embodiment, an antiferromagnetic layer is provided on the heavy metal layer, and the magnetic anisotropy of the left and right half regions of the antiferromagnetic layer is different, thereby realizing a step magnetic anisotropy structure design; the spin-orbit torque generated by the current in the heavy metal layer is used to drive the antiferromagnetic Neel wall from the high magnetic anisotropy region to the low magnetic anisotropy region, and the equivalent potential energy at the step is converted into kinetic energy. At a low current density (e.g., 10 10 A / m 2 ) drives the domain wall to move close to the saturation speed, and the domain wall undergoes Lorentz contraction, generating spin waves in the THz band. It not only has low current density, low power consumption, and high frequency (2 to 4 THz), but is also compatible with semiconductor processes, providing a reliable and efficient new way to realize high-frequency THz magnon generators.

[0042] On the basis of the above embodiment, the difference between the magnetic anisotropy of the left half region and the right half region in this embodiment is an optimal difference, so that the critical current density of the domain wall emitting magnetons is minimized.

[0043] This embodiment introduces a process of converting potential energy into kinetic energy through structural innovation, which can make the domain wall motion speed close to the saturation speed under low current, thereby emitting THz magnetons. Compared with the non-anisotropic step, the critical current density can be reduced to about 1 / 3 (when ΔK = 0.4 meV), as shown in Figure 2. Figure 3 As shown in Figure (a).

[0044] For example, when the magnetic anisotropy K1 in the left half of the region is greater than the magnetic anisotropy K2 in the right half, and K2 is held constant at 0.04 meV, the critical current density first decreases and then increases as K1 increases. The initial decrease is due to the increase in ΔK as the domain wall passes over the step, allowing the greater magnetic anisotropy to be converted into kinetic energy. The subsequent increase is due to the fact that as K1 increases, the critical current density required to propel the domain wall becomes greater. Therefore, there exists an optimal difference ΔK that minimizes the critical current density for emitting magnons.

[0045] Based on the above embodiment, the step of obtaining the optimal difference in this embodiment includes:

[0046] Obtaining a relationship curve between the difference and the critical current density of the domain wall emitting magnons through simulation;

[0047] The difference corresponding to the minimum critical current density in the relationship curve is used as the optimal difference.

[0048] For example, the relationship curve between the difference ΔK and the critical current density of the domain wall emitting magnons is obtained through simulation as follows: Figure 3 As shown in Figure (a), ΔK = 0.4 meV is the optimal difference from the relationship curve, and the critical current density corresponding to the optimal difference in the relationship curve is the minimum critical current density.

[0049] Based on the above embodiment, in this embodiment, in the simulation, the magnetic anisotropy of the region with low magnetic anisotropy remains unchanged, and the magnetic anisotropy of the region with high magnetic anisotropy gradually increases. The difference is calculated each time the magnetic anisotropy increases, and the current is gradually increased until the domain wall emits magnons, and the critical current density is calculated based on the increased current.

[0050] For example, when the magnetic anisotropy K1 in the left half of the region is greater than the magnetic anisotropy K2 in the right half of the region, keeping K2 = 0.04 meV unchanged, as K1 increases, the difference ΔK gradually increases, and the critical current density first decreases and then increases. According to the critical current density corresponding to each difference ΔK, the following is plotted: Figure 3 The relationship curve shown in Figure (a).

[0051] On the basis of the above embodiment, in this embodiment, the frequency of the domain wall emitting magnetons is controlled by regulating the difference between the magnetic anisotropy of the left half region and the right half region, or the magnitude of the current.

[0052] The frequency of emitted magnons can be controlled by adjusting the difference ΔK. The frequency of emitted magnons can also be dynamically controlled by changing the magnitude of the current J.

[0053] In this embodiment, the spin wave frequency can be dynamically controlled by various means.

[0054] Based on the above embodiment, the step of controlling the frequency of the domain wall emitting magnetons in this embodiment includes:

[0055] Under the condition that the magnitude of the current remains unchanged, obtaining a relationship curve between the frequency of the domain wall emitting magnetons and the difference through simulation;

[0056] According to the relationship curve, obtaining a difference corresponding to a target frequency of the domain wall emitting magnetons;

[0057] The difference between the magnetic anisotropy of the left half region and the right half region is adjusted to be a difference corresponding to the target frequency, so that the frequency of the domain wall emitting magnetic particles is the target frequency.

[0058] For example, the relationship curve between the frequency of domain wall emission and the difference ΔK obtained by simulation is as follows: Figure 3 As shown in Figure (b), as the difference ΔK increases, the frequency of domain wall magnon emission gradually decreases. Based on this relationship curve, the difference ΔK is controlled to make the frequency of domain wall magnon emission reach the target frequency.

[0059] Based on the above embodiment, the step of controlling the frequency of the domain wall emitting magnetons in this embodiment includes:

[0060] Under the condition that the difference remains unchanged, obtaining a relationship curve between the frequency of the domain wall emitting magnetons and the current density of the current through simulation;

[0061] According to the relationship curve, a current density corresponding to a target frequency of the domain wall emitting magnetons is obtained;

[0062] The magnitude of the current is regulated so that the current density of the current is the current density corresponding to the target frequency, so that the frequency of the domain wall emitting magnetons is the target frequency.

[0063] For example, when K1 = 0.44 meV, K2 = 0.04 meV, the relationship curve between the frequency of domain wall emission and current density is obtained through simulation as follows: Figure 4 As shown in Figure 1, as the current density increases, the frequency of the domain wall emitting magnons gradually decreases. According to this relationship curve, the current size is regulated to change the current density so that the frequency of the domain wall emitting magnons reaches the target frequency.

[0064] On the basis of the above embodiments, in this embodiment, the material used for the heavy metal layer is Pt or Ta, and the material used for the antiferromagnetic layer is NiO or α-Fe2O3 or other antiferromagnetic materials.

[0065] Based on the above embodiments, the different magnitudes of magnetic anisotropy between the left half region and the right half region in this embodiment are achieved through interface design, process control or voltage-controlled magnetic anisotropy (VCMA) effect.

[0066] On the basis of the above embodiments, in this embodiment, the magnetic anisotropy of the left half region is greater than the magnetic anisotropy of the right half region.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A THz magnon generator based on high-speed motion of antiferromagnetic domain walls, characterized in that: include: Heavy metal layer; an antiferromagnetic layer, the antiferromagnetic layer being located on the heavy metal layer, wherein the magnetic anisotropy of the left half region and the right half region of the antiferromagnetic layer are different in magnitude; applying a current in the heavy metal layer to generate a spin-orbit torque; The spin-orbit torque drives the Neely wall in the antiferromagnetic layer to move from the region with high magnetic anisotropy to the region with low magnetic anisotropy; when the domain wall in the antiferromagnetic layer passes through the junction of the left half region and the right half region, the equivalent potential energy of the magnetic anisotropy is converted into kinetic energy, driving the domain wall to move at a speed close to the saturation speed, causing the domain wall to undergo Lorentz contraction and emit spin waves in the THz frequency band.

2. The THz magneton generator based on high-speed motion of antiferromagnetic domain walls according to claim 1, characterized in that: The difference between the magnetic anisotropy of the left half region and the right half region is an optimal difference, so that the critical current density of the domain wall emitting magnetons is minimized.

3. The THz magneton generator based on high-speed motion of antiferromagnetic domain walls according to claim 2, characterized in that: The step of obtaining the optimal difference comprises: Obtaining a relationship curve between the difference and the critical current density of the domain wall emitting magnons through simulation; The difference corresponding to the minimum critical current density in the relationship curve is used as the optimal difference.

4. The THz magneton generator based on high-speed motion of antiferromagnetic domain walls according to claim 3, characterized in that: In the simulation, the magnetic anisotropy of the region with low magnetic anisotropy remains unchanged, while the magnetic anisotropy of the region with high magnetic anisotropy gradually increases. The difference is calculated each time the magnetic anisotropy increases, and the current is gradually increased until the domain wall emits magnons. The critical current density is calculated based on the increased current.

5. The THz magnon generator based on high-speed motion of antiferromagnetic domain walls according to claim 1, characterized in that: The frequency of the domain wall emitting magnetons is controlled by regulating the difference between the magnetic anisotropy of the left half region and the right half region, or the magnitude of the current.

6. The THz magnon generator based on high-speed motion of antiferromagnetic domain walls according to claim 5, characterized in that: The step of regulating the frequency of the domain wall emitting magnetons comprises: Under the condition that the magnitude of the current remains unchanged, obtaining a relationship curve between the frequency of the domain wall emitting magnetons and the difference through simulation; According to the relationship curve, obtaining a difference corresponding to a target frequency of the domain wall emitting magnetons; The difference between the magnetic anisotropy of the left half region and the right half region is adjusted to be a difference corresponding to the target frequency, so that the frequency of the domain wall emitting magnetic particles is the target frequency.

7. The THz magnon generator based on high-speed motion of antiferromagnetic domain walls according to claim 5, characterized in that: The step of regulating the frequency of the domain wall emitting magnetons comprises: Under the condition that the difference remains unchanged, obtaining a relationship curve between the frequency of the domain wall emitting magnetons and the current density of the current through simulation; According to the relationship curve, a current density corresponding to a target frequency of the domain wall emitting magnetons is obtained; The magnitude of the current is regulated so that the current density of the current is the current density corresponding to the target frequency, so that the frequency of the domain wall emitting magnetons is the target frequency.

8. The THz magnon generator based on high-speed motion of antiferromagnetic domain walls according to any one of claims 1 to 7, characterized in that: The material used for the heavy metal layer is Pt, and the material used for the antiferromagnetic layer is NiO or α-Fe2O3.

9. The THz magnon generator based on high-speed motion of antiferromagnetic domain walls according to any one of claims 1 to 7, characterized in that: The difference in magnitude of the magnetic anisotropy between the left half region and the right half region is achieved through interface design, process control or voltage-controlled magnetic anisotropy effect.

10. The THz magnon generator based on high-speed motion of antiferromagnetic domain walls according to any one of claims 1 to 7, characterized in that: The magnetic anisotropy of the left half region is greater than the magnetic anisotropy of the right half region.

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