Skyrmion track memory based on artificial ferromagnet

Abstract

The invention discloses a skyrmion track memory based on an artificial ferromagnet, and belongs to the technical field of spintronics and nano magnetic devices. The device comprises a heavy metal layer, an artificial ferromagnet layer and a read-write end, the artificial ferromagnet layer is composed of a plurality of parallel Skyrmion strip-shaped racing tracks. Each Skyrmion strip-shaped racing track comprises a lower ferromagnetic film, a non-magnetic middle layer and an upper ferromagnetic film, the upper ferromagnetic film and the lower ferromagnetic film are made of magnetic materials with different saturation magnetization intensities, and the net magnetization intensities of the adjacent Skyrmion strip-shaped racing tracks are positive and negative, so that the Skyrmion in the adjacent racing tracks deflect in opposite directions. The two opposite lateral displacements cancel each other at the boundary, causing the magnetic skyrmion to move along the boundary. According to the invention, the problem of inaccurate positioning caused by the Hall effect of the Skyrmion is solved, the read-write precision, reliability and expandability of the device are remarkably improved, and powerful technical support is provided for high-performance development and practical application of the Skyrmion track memory.

Description

Technical Field

[0001] This invention belongs to the field of spintronics and nanomagnetic devices, specifically relating to a skyrmion track memory based on an artificial subferromagnet. Background Technology

[0002] With the rapid development of today's information society, the demand for data storage is exploding, posing numerous challenges to traditional storage technologies. Magnetic storage technology, as one of the mainstream storage methods, is widely used due to its non-volatility, high capacity, and relatively low cost. However, traditional magnetic storage devices, such as hard disk drives and magnetic random access memory, are gradually approaching their physical limits in terms of performance and scalability.

[0003] Skyrmions, as a novel type of topological magnetic structure, have attracted considerable attention due to their unique physical properties. Skyrmions are magnetic vortex structures with topological protection characteristics, exhibiting small size, high stability, ease of manipulation, and the ability to achieve rapid information reading and writing with low energy consumption. Skyrmion track memory utilizes the movement and manipulation of skyrmions within magnetic materials to achieve data storage and retrieval, and is considered a highly promising next-generation storage technology. However, in the practical application of skyrmion track memory, the skyrmion Hall effect has become a critical problem that urgently needs to be solved.

[0004] The skyrmion Hall effect refers to the lateral displacement phenomenon, similar to the Hall effect, that occurs when skyrmions move in a magnetic material under the influence of an electric current, deviating from their driving direction. This displacement makes it difficult to precisely control the position of skyrmions in a race track, thus affecting the read / write accuracy and reliability of the memory. Therefore, effectively suppressing the skyrmion Hall effect and achieving precise control of skyrmions is one of the key challenges for the practical application of skyrmion race track memory. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to propose a skyrmion track memory based on an artificial subferromagnet. The memory comprises multiple parallel skyrmion strip tracks, with adjacent skyrmion strip tracks exhibiting opposite net magnetization intensities. This causes the radial forces provided at the boundaries to cancel each other out, ensuring that skyrmions can only move along their boundaries. This counteracts the skyrmion Hall effect and provides strong technical support for the high-performance development and practical application of skyrmion track memories.

[0006] The technical solution adopted in this invention is as follows: A skymin subtrack memory based on an artificial ferrimagnet includes a heavy metal layer, an artificial ferrimagnet layer, and a read / write terminal arranged from bottom to top. The artificial ferrimagnet layer consists of at least three parallel skyrmion strip tracks; The skyrmion strip track comprises a lower ferromagnetic thin film, a non-magnetic intermediate layer, and an upper ferromagnetic thin film arranged sequentially from bottom to top. The lower and upper ferromagnetic thin films are magnetic materials with different saturation magnetizations. The non-magnetic intermediate layer provides RKKY interaction, thereby achieving antiferromagnetic coupling between the two ferromagnetic thin films and forming an artificial subferromagnet. Simultaneously, the net magnetizations of adjacent skyrmion strip tracks are positive and negative, causing skyrmions in adjacent strip tracks to deflect in opposite directions. These two opposite lateral displacements cancel each other out at the boundary, allowing the magnetic skyrmions to move along the boundary. The read / write end includes a read end and a write end, wherein the write end is a magnetic tunnel junction located directly above the skyrmion strip track, which writes artificial ferrimagnetic skyrmions by applying a pulse current; the read end is a magnetic tunnel junction located directly above the intersection of the skyrmion strip track, which reads skyrmions by measuring magnetoresistance.

[0007] Preferably, the materials of the lower ferromagnetic thin film and the upper ferromagnetic thin film are one of the following: iron, cobalt, nickel, iron-silicon alloy, iron-nickel alloy, samarium-cobalt alloy, iron-platinum alloy, iron-palladium alloy, magnetite, manganese-zinc ferrite, nickel ferrite, nickel-zinc ferrite, cobalt ferrite, and cobalt-iron-boron materials.

[0008] Preferably, the material of the non-magnetic intermediate layer is a 4d / 5d non-magnetic transition metal, such as ruthenium, rhodium, chromium, etc.

[0009] Preferably, the heavy metal layer is made of platinum, iridium, tungsten, etc., to provide DM interaction, thereby stabilizing the magnetic skyrmions in the artificial ferrimagnet layer.

[0010] Preferably, the width of the skyrmion strip track is in the range of 30~100 nm.

[0011] Preferably, the thickness of the lower ferromagnetic film is in the range of 1~10 nm; the thickness of the upper ferromagnetic film is in the range of 1~10 nm; and the thickness of the non-magnetic intermediate layer is in the range of 1~10 nm.

[0012] Preferably, the shape of the scrimmage strip track is straight, curved, or circular (circular, rectangular, track-shaped, etc.).

[0013] Preferably, the read / write speed of the skyrmion track memory is controlled by changing the magnitude of the driving current of the skyrmion track memory, thereby controlling the speed of the skyrmion at the artificial subferromagnetic boundary.

[0014] Preferably, different processing techniques are used to prepare the lower and upper ferromagnetic thin films, thereby controlling the magnitude of Gilbert damping in the ferromagnetic thin film, regulating the speed of skyrmions at the artificial subferromagnetic boundary, and thus regulating the read and write speed of the skyrmion track memory.

[0015] Preferably, the heavy metal layer, the lower ferromagnetic thin film, the non-magnetic intermediate layer, and the upper ferromagnetic thin film are prepared by different processing techniques, such as magnetron sputtering, molecular beam epitaxy, or pulsed laser beam deposition.

[0016] The present invention has the following beneficial effects: (1) The present invention uses artificial ferrimagnets to prepare skymintz track memory. Compared with traditional ferrimagnetic materials, artificial ferrimagnets have higher design flexibility and controllability, while reducing the difficulty of industrial production.

[0017] (2) The skyrmion track memory of the present invention contains multiple skyrmion strip tracks arranged in parallel. The net magnetization intensity of adjacent skyrmion strip tracks is positive and negative. It cleverly utilizes the fact that the skyrmion Hall angle is different under different artificial ferrimagnets. The two opposite lateral displacements cancel each other out at the boundary, so that the skyrmion moves along the boundary, thereby effectively canceling the skyrmion Hall effect.

[0018] (2) In the skyrmion track memory of the present invention, the speed of the skyrmion can be controlled by various means, such as the magnitude of the driving current and the material Gilbert damping, to adapt to high-speed cache and storage-computing integration; the maximum speed of the skyrmion of the present invention can reach 580 m / s, which significantly improves the performance of the memory.

[0019] (3) The skyrmion track memory of the present invention can also realize the movement of skyrmions along the ring boundary, which greatly enhances the ability to precisely control skyrmions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the skyrmion track memory based on artificial ferrimagnets according to the present invention.

[0021] Figure 2 This is a schematic diagram of the ferromagnetic thin film layout of adjacent skyrmion strip tracks in this invention.

[0022] Figure 3 This is a magnetic moment distribution diagram of skyrmions in the upper and lower ferromagnetic thin films of the present invention.

[0023] Figure 4 This is the trajectory of a skyrmion in a single artificial subferromagnetic track in Embodiment 1 of the present invention.

[0024] Figure 5This is the trajectory of the skyrmion in the coupled artificial subferromagnetic track in Embodiment 1 of the present invention.

[0025] Figure 6 This is a graph showing the relationship between the speed of the skyrmion and the magnitude of the driving current in Embodiment 1 of the present invention.

[0026] Figure 7 This is a graph showing the relationship between skyrmion velocity and the magnitude of material Gilbert damping in Embodiment 1 of the present invention.

[0027] Figure 8 This is a graph showing the relationship between skyrmion velocity and the coupling strength between artificial subferromagnetic layers in Embodiment 1 of the present invention.

[0028] Figure 9 This is a trajectory diagram of the skyrmion moving at the circular boundary in Embodiment 2 of the present invention.

[0029] Explanation of reference numerals in the attached diagram: 1. Heavy metal layer, 2. Lower ferromagnetic thin film, 3. Non-magnetic intermediate layer, 4. Upper ferromagnetic thin film, 5. Write end, 6. Read end. Detailed Implementation

[0030] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. Example 1

[0031] This embodiment provides a skymin subtrack memory based on an artificial subferromagnet, such as Figure 1 As shown, the device includes a heavy metal layer, an artificial ferrimagnet layer, and read / write terminals arranged sequentially from bottom to top. The heavy metal layer is a 1 nm thick platinum thin film. The artificial ferrimagnet layer consists of three parallel skyrmion strip tracks, each track being 50 nm wide. The read / write terminals include three write terminals and two read terminals. The write terminals are magnetic tunnel junctions with a diameter of 20 nm, located directly above each skyrmion strip track. The read terminals are magnetic tunnel junctions with a diameter of 40 nm, located at the junctions of the skyrmion strip tracks.

[0032] The skyrmion strip track comprises a lower ferromagnetic thin film, a non-magnetic intermediate layer, and an upper ferromagnetic thin film arranged sequentially from bottom to top, each with a thickness of 1 nm. The lower and upper ferromagnetic thin films are magnetic materials with different saturation magnetization intensities. The non-magnetic intermediate layer provides RKKY interaction, thereby achieving antiferromagnetic coupling between the upper and lower ferromagnetic thin films to form an artificial subferromagnet.

[0033] like Figure 2 As shown, to achieve a net magnetization of opposite polarities for adjacent skyrmion strip tracks, in this embodiment, the upper ferromagnetic film of the two side skyrmion strip tracks is ferromagnetic film a, and the lower ferromagnetic film is ferromagnetic film b; the upper ferromagnetic film of the middle skyrmion strip track is ferromagnetic film b, and the lower ferromagnetic film is ferromagnetic film a; that is, in the same layer, ferromagnetic film a and ferromagnetic film b are arranged alternately. In this embodiment, the material of the non-magnetic intermediate layer is the non-magnetic metal ruthenium, the material of ferromagnetic film a is the magnetic metal cobalt, and the material of ferromagnetic film b is the magnetic metal cobalt-iron-boron. Figure 3 The magnetic moment distribution diagrams of skyrmions in ferromagnetic thin films b and a within the central skyrmion strip track are shown.

[0034] In the central skyrmion strip track, due to the skyrmion Hall effect, the skyrmions within it will move along the deflection direction at the lower right corner, such as... Figure 4 As shown in (a), the lower ferromagnetic film is ferromagnetic film a, i.e., magnetic metal cobalt, and the upper ferromagnetic film is ferromagnetic film b, i.e., magnetic metal cobalt-iron-boron. The arrows indicate the direction of the background magnetic moment (i.e., the magnetic moment surrounding the skyrmion). In the skyrmion strip tracks on both sides, due to the flipping of the magnetic film, the skyrmions inside will move along the direction of the upper right corner, as shown in (a). Figure 4 As shown in (b), the upper ferromagnetic film is ferromagnetic film a, i.e., magnetic metal cobalt, and the lower ferromagnetic film is ferromagnetic film b, i.e., magnetic metal cobalt-iron-boron. The arrows indicate the direction of the background magnetic moment (i.e., the magnetic moment surrounding the skyrmion). That is, skyrmions in adjacent strip tracks deflect in opposite directions.

[0035] like Figure 5 As shown, driven by an electric current, skyrmions initially move downwards and to the right due to the skyrmion Hall effect. Subsequently, at the boundary of the adjacent skyrmion strip tracks ( y = -25 nm), due to the Hall effect of skyrmions on both sides, the skyrmions will first oscillate up and down along the boundary until... y The velocity in the direction is canceled out, and finally it moves in a straight line along the boundary. At this point, the skyrmion Hall effect is completely canceled out, thus achieving precise control of the skyrmion.

[0036] Applying spin-polarized currents of varying densities to drive the skyrmions in the skyrmion track memory, such as... Figure 6 As shown in the figure, the horizontal axis represents the current density of the driving current, and the vertical axis represents the velocity of the skyrmion. It can be seen that the skyrmion velocity and the magnitude of the current density exhibit a linear relationship. When the current density is 500 MA / cm²... 2 At that time, the speed of skyrmions can reach 580 m / s, which provides an excellent platform for high-speed information processing.

[0037] Furthermore, by employing different fabrication processes and optimizing the Gilbert damping of the material, the motion velocity of skyrmions can be further enhanced. For example... Figure 7 As shown in the figure, the horizontal axis represents the reciprocal of Gilbert damping, and the vertical axis represents the speed of skyrmion motion. It can be seen that the speed of skyrmion motion is linearly related to the reciprocal of Gilbert damping, that is, the smaller the Gilbert damping of the material, the faster the speed of skyrmion motion.

[0038] In addition, such as Figure 8 As shown, the horizontal axis represents the strength of interlayer exchange coupling in the artificial ferrimagnet, and the vertical axis represents the speed of skyrmion motion. The speed of skyrmion is not very sensitive to the magnitude of interlayer RKKY interaction, which is controlled by the thickness of the non-magnetic interlayer. This means that even if the thickness of the non-magnetic interlayer is uneven, the speed of skyrmion will not fluctuate significantly. This is of great significance for the stability of skyrmion motion and reducing the difficulty of material processing. Example 2

[0039] In this embodiment, the structures from Embodiment 1 are connected end to end to form a circular track memory, such as... Figure 9 As shown, the inner radius of the ring is 100 nm and the outer radius is 250 nm.

[0040] When a clockwise-directed toroidal spin-polarized current is applied, since the electrons move in a counter-clockwise direction, skyrmions will also move in a counter-clockwise direction, such as... Figure 9 As shown in (a), the skyrmions gradually deflect to the boundary of the coupled artificial ferrimagnet (a circle with a radius of 200 nm) due to the skyrmion Hall effect. Then, as in Example 1, the skyrmions oscillate in the radial direction perpendicular to the boundary and then move in a circle along the boundary.

[0041] When a counter-clockwise toroidal spin-polarized current is applied, the skyrmions will move in a clockwise circular motion at the boundary of the coupled artificial ferrimagnet (a circle with a radius of 150 nm), as... Figure 9 As shown in (b) above. It can be seen that this invention can realize the movement of skyrmions along a circular boundary, thereby controlling the velocity direction of the skyrmions, which is of great significance for the precise control of skyrmions in information storage.

[0042] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A skymin subtrack memory based on an artificial subferromagnet, characterized in that, It includes a heavy metal layer, an artificial ferrimagnet layer, and a read / write terminal arranged from bottom to top; The artificial ferrimagnet layer consists of at least three parallel skyrmion strip tracks; The skyrmion strip track comprises a lower ferromagnetic thin film, a non-magnetic intermediate layer, and an upper ferromagnetic thin film arranged sequentially from bottom to top. The lower and upper ferromagnetic thin films are magnetic materials with different saturation magnetizations. The non-magnetic intermediate layer provides RKKY interaction, thereby achieving antiferromagnetic coupling between the two ferromagnetic thin films and forming an artificial subferromagnet. Simultaneously, the net magnetizations of adjacent skyrmion strip tracks are positive and negative, causing skyrmions in adjacent strip tracks to deflect in opposite directions. These two opposite lateral displacements cancel each other out at the boundary, allowing the magnetic skyrmions to move along the boundary. The read / write end includes a read end and a write end, wherein the write end is a magnetic tunnel junction located directly above the skyrmion strip track, which writes artificial ferrimagnetic skyrmions by applying a pulse current; the read end is a magnetic tunnel junction located directly above the intersection of the skyrmion strip track, which reads skyrmions by measuring magnetoresistance.

2. The skyrmion track memory based on an artificial subferromagnet as described in claim 1, characterized in that, The materials of the lower ferromagnetic thin film and the upper ferromagnetic thin film are one of the following: iron, cobalt, nickel, iron-silicon alloy, iron-nickel alloy, samarium-cobalt alloy, iron-platinum alloy, iron-palladium alloy, magnetite, manganese-zinc ferrite, nickel ferrite, nickel-zinc ferrite, cobalt ferrite, and cobalt-iron-boron materials.

3. The skyrmion track memory based on an artificial ferrimagnet as described in claim 1, characterized in that, The material of the non-magnetic intermediate layer is a 4d / 5d non-magnetic transition metal.

4. A skymin subtrack memory based on an artificial ferrimagnet as described in claim 1, characterized in that, The material of the heavy metal layer is platinum, iridium, or tungsten.

5. A skymin subtrack memory based on an artificial subferromagnet as described in any one of claims 1-4, characterized in that, The width of the skyrmion strip track ranges from 30 to 100 nm.

6. A skymin subtrack memory based on an artificial subferromagnet as described in claim 5, characterized in that, The thickness of the lower ferromagnetic thin film ranges from 1 to 10 nm; the thickness of the upper ferromagnetic thin film ranges from 1 to 10 nm; and the thickness of the non-magnetic intermediate layer ranges from 1 to 10 nm.

7. A skymin subtrack memory based on an artificial subferromagnet as described in claim 6, characterized in that, The shape of the skyminzi strip track can be straight, curved, or circular.

8. A skymin subtrack memory based on an artificial ferrimagnet as described in claim 7, characterized in that, By changing the magnitude of the driving current of the skyrmion track memory, the speed of the skyrmion at the artificial subferromagnetic boundary can be controlled, thereby controlling the read and write speed of the skyrmion track memory.

9. A skymin subtrack memory based on an artificial subferromagnet as described in claim 7, characterized in that, By employing different processing techniques to prepare the lower and upper ferromagnetic thin films, the magnitude of Gilbert damping in the ferromagnetic thin film can be controlled, thereby regulating the speed of skyrmions at the artificial subferromagnetic boundary and ultimately controlling the read / write speed of the skyrmion track memory.

10. A skymin subtrack memory based on an artificial subferromagnet as described in claim 1, characterized in that, The heavy metal layer, the lower ferromagnetic thin film, the non-magnetic intermediate layer, and the upper ferromagnetic thin film are prepared by magnetron sputtering, molecular beam epitaxy, or pulsed laser beam deposition.

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