A skyrmion racetrack memory based on artificial ferrimagnet

Abstract

The application discloses a skyrmion racetrack memory based on artificial ferrimagnet, and belongs to the technical field of spin electronics and nanomagnetic devices. The device comprises a heavy metal layer, an artificial ferrimagnet layer and a read-write end; the artificial ferrimagnet layer is composed of a plurality of parallel skyrmion strip racetracks; the skyrmion strip racetrack comprises a lower ferromagnetic film, a non-magnetic intermediate layer and an upper ferromagnetic film; the upper and lower ferromagnetic films are magnetic materials with different saturation magnetization intensities; and the net magnetization intensities of adjacent skyrmion strip racetracks are positive and negative, so that skyrmions in adjacent racetracks are deflected in opposite directions, and the two opposite transverse displacements are offset at the boundary, so that the magnetic skyrmions move along the boundary. The application solves the problem of inaccurate positioning caused by the skyrmion Hall effect, significantly improves the read-write precision, reliability and scalability of the device, and provides strong technical support for the high-performance development and practical application of the skyrmion racetrack memory.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of spintronics and nanomagnetic devices, and particularly relates to a skyrmion racetrack memory based on an artificial ferrimagnet. BACKGROUND

[0002] With the rapid development of the current information society, the demand for data storage is showing an explosive growth, and the traditional storage technology is facing many challenges. As one of the mainstream storage methods, magnetic storage technology 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 memories, are gradually approaching their physical limits in terms of performance and scalability.

[0003] Skyrmions, as a new type of topological magnetic structure, have attracted much attention due to their unique physical properties. Skyrmions are a kind of magnetic vortex structure with topological protection characteristics, which are small in size, high in stability, easy to manipulate, and can realize fast information reading and writing at low energy consumption. Skyrmion racetrack memory utilizes the movement and manipulation of skyrmions in magnetic materials to realize data storage and reading, and is considered as a potential next-generation storage technology. However, in the practical application of skyrmion racetrack memory, the skyrmion Hall effect has become a key problem to be solved.

[0004] The skyrmion Hall effect refers to the phenomenon that, under the driving of electric current, skyrmions deviate from their driving direction when moving in magnetic materials, showing a transverse shift similar to the Hall effect. This shift makes it difficult to accurately control the position of skyrmions in the racetrack, thereby affecting the reading and writing accuracy and reliability of the memory. Therefore, how to effectively suppress the skyrmion Hall effect and realize the precise manipulation of skyrmions is one of the key challenges for the practical application of skyrmion racetrack memory. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application aims to provide a skyrmion racetrack memory based on an artificial ferrimagnet. The memory of the present application comprises a plurality of parallel arranged skyrmion strip racetracks, and the net magnetization intensity in adjacent skyrmion strip racetracks is positive and negative, respectively, so as to provide a mutual cancellation of the radial force of skyrmions at the boundary, thereby making the skyrmions only move along the boundary, and canceling the skyrmion Hall effect, thereby providing strong technical support for the high-performance development and practical application of skyrmion racetrack memory.

[0006] The technical scheme adopted by the present application is as follows:

[0007] A skyrmion racetrack memory based on an artificial ferrimagnet, comprising a heavy metal layer, an artificial ferrimagnet layer and a read-write end arranged from bottom to top.

[0008] The artificial ferrimagnetic layer is composed of at least three parallelly arranged SGM racetracks.

[0009] The SGM racetrack comprises, from bottom to top, a lower ferromagnetic film, a non-magnetic intermediate layer and an upper ferromagnetic film; the lower ferromagnetic film and the upper ferromagnetic film are magnetic materials with different saturation magnetization, and the non-magnetic intermediate layer provides RKKY interaction to realize the antiferromagnetic coupling between the upper and lower ferromagnetic films, thereby constructing an artificial ferrimagnet; meanwhile, the net magnetization of adjacent SGM racetracks is positive and negative, so that the SGMs in adjacent racetracks deflect in opposite directions, and the two opposite lateral displacements cancel each other out at the boundary, thereby enabling the magnetic SGMs to move along the boundary.

[0010] The read-write end comprises a read end and a write end, wherein the write end is a magnetic tunnel junction located directly above the SGM racetrack, and the artificial ferrimagnetic SGM is written by applying a pulse current; the read end is a magnetic tunnel junction located directly above the junction of the SGM racetrack, and the SGM is read by measuring the magnetoresistance.

[0011] Preferably, the materials of the lower ferromagnetic film and the upper ferromagnetic film are one of 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 material.

[0012] Preferably, the material of the non-magnetic intermediate layer is a 4d / 5d non-magnetic transition metal; for example, ruthenium, rhodium, chromium, etc.

[0013] Preferably, the material of the heavy metal layer is platinum, iridium, tungsten, etc., which is used to provide DM interaction to stabilize the magnetic SGMs in the artificial ferrimagnetic layer.

[0014] Preferably, the width of the SGM racetrack ranges from 30 nm to 100 nm.

[0015] Preferably, the thickness of the lower ferromagnetic film ranges from 1 nm to 10 nm; the thickness of the upper ferromagnetic film ranges from 1 nm to 10 nm; and the thickness of the non-magnetic intermediate layer ranges from 1 nm to 10 nm.

[0016] Preferably, the shape of the SGM racetrack is linear, curved or ring-shaped (circular ring, rectangular ring, racetrack-shaped ring, etc.).

[0017] Preferably, the driving current of the SGM racetrack memory is changed to control the movement speed of the SGMs at the artificial ferrimagnetic boundary, thereby controlling the read-write speed of the SGM racetrack memory.

[0018] Preferably, the lower ferromagnetic film and the upper ferromagnetic film are prepared by different processing techniques, so as to control the Gilbert damping in the ferromagnetic film, regulate the movement speed of the skyrmion at the artificial ferrimagnetic boundary, and further regulate the read-write speed of the skyrmion racetrack memory.

[0019] Preferably, the heavy metal layer, the lower ferromagnetic film, the non-magnetic intermediate layer, and the upper ferromagnetic film are prepared by different processing techniques, such as magnetron sputtering, molecular beam epitaxy, or pulsed laser deposition.

[0020] The present application has the following beneficial effects:

[0021] (1) The present application uses an artificial ferrimagnet to prepare a skyrmion racetrack memory, which has higher design flexibility and controllability compared with traditional ferrimagnetic materials, and reduces the difficulty of industrial production.

[0022] (2) The skyrmion racetrack memory of the present application comprises a plurality of parallel arranged skyrmion strip racetracks, and the net magnetization intensity in adjacent skyrmion strip racetracks is positive and negative, which ingeniously utilizes the different skyrmion Hall angles of skyrmions under different artificial ferrimagnets, and the two opposite lateral displacements cancel each other out at the boundary, so that the skyrmions move along the boundary, thereby effectively canceling the skyrmion Hall effect.

[0023] (2) In the skyrmion racetrack memory of the present application, the speed of the skyrmion can be regulated by various means, such as the size of the driving current, the material Gilbert damping, etc., to adapt to high-speed caching and integrated storage and calculation; the highest speed of the skyrmion of the present application can reach 580 m / s, which significantly improves the performance of the memory.

[0024] (3) The skyrmion racetrack memory of the present application can also realize the movement of skyrmions along the ring-shaped boundary, which greatly enhances the precise control ability of skyrmions. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 FIG. 1 is a structural schematic diagram of the skyrmion racetrack memory based on artificial ferrimagnet of the present application.

[0026] Figure 2 FIG. 4 is a schematic diagram of the ferromagnetic film layout of adjacent skyrmion strip racetracks in the present application.

[0027] Figure 3 FIG. 6 is a magnetic moment distribution diagram of skyrmions in the upper ferromagnetic film and the lower ferromagnetic film in the present application.

[0028] Figure 4 FIG. 8 is a movement trajectory of skyrmions in a single artificial ferrimagnetic racetrack in Example 1 of the present application.

[0029] Figure 5 Trajectory of the skyrmion in the embodiment 1 of the present application in the race of the artificial ferrimagnetic track.

[0030] Figure 6 The relationship between the skyrmion velocity and the Gilbert damping in the embodiment 1 of the present application.

[0031] Figure 7 The relationship between the skyrmion velocity and the coupling strength between the artificial ferrimagnetic layers in the embodiment 1 of the present application.

[0032] Figure 8 The relationship between the skyrmion velocity and the coupling strength between the artificial ferrimagnetic layers in the embodiment 1 of the present application.

[0033] Figure 9 Trajectory of the skyrmion in the embodiment 2 of the present application in the race of the artificial ferrimagnetic track.

[0034] BRIEF DESCRIPTION OF DRAWINGS 1. Heavy metal layer, 2. Lower ferromagnetic film, 3. Non-magnetic intermediate layer, 4. Upper ferromagnetic film, 5. Writing end, 6. Reading end. DETAILED DESCRIPTION

[0035] The present application is described herein with reference to specific embodiments thereof which are illustrated in the attached drawings. These embodiments are described in detail so as to enable others skilled in the art to most readily utilize the application in accordance with the embodiments described but it is understood that those skilled in the art, upon attaining an understanding of the nature of the application, can readily acquire the requisite knowledge of structure and functionality without undue experimentation, and can therefore apply the application broadly to variants of the specific embodiments herein described, and to equivalents thereof, without doing so falling outside the spirit and scope of the application. Various modifications and changes can be made thereto by those skilled in the art which pertain particularly to different embodiments without departing from the spirit and scope of the application. Embodiment 1

[0036] The embodiment provides a skyrmion race track memory based on an artificial ferrimagnet, as shown in the figure, comprising a heavy metal layer, an artificial ferrimagnet layer and a read-write end arranged in sequence from bottom to top; wherein the heavy metal layer is a metal platinum film with a thickness of 1 nm; the artificial ferrimagnet layer is composed of three parallel arranged skyrmion strip tracks, and the width of each track is 50 nm; the read-write end comprises 3 writing ends and 2 reading ends, the writing end is a magnetic tunnel junction with a diameter of 20 nm, located directly above each skyrmion strip track, and the reading end is a magnetic tunnel junction with a diameter of 40 nm, located at the junction of the skyrmion strip track. Figure 1 The skyrmion strip track comprises a lower ferromagnetic film, a non-magnetic intermediate layer and an upper ferromagnetic film arranged in sequence from bottom to top, and the thicknesses of the three layers are all 1 nm; the lower ferromagnetic film and the upper ferromagnetic film are magnetic materials with different saturation magnetization strengths, and the RKKY interaction is provided through the non-magnetic intermediate layer to realize the antiferromagnetic coupling between the upper and lower ferromagnetic films, thereby constructing an artificial ferrimagnet.

[0037] The skyrmion strip track comprises a lower ferromagnetic film, a non-magnetic intermediate layer and an upper ferromagnetic film arranged in sequence from bottom to top, and the thicknesses of the three layers are all 1 nm; the lower ferromagnetic film and the upper ferromagnetic film are magnetic materials with different saturation magnetization strengths, and the RKKY interaction is provided through the non-magnetic intermediate layer to realize the antiferromagnetic coupling between the upper and lower ferromagnetic films, thereby constructing an artificial ferrimagnet.

[0038] As Figure 2 shown, in order to realize the net magnetization of adjacent skyrmion racetracks being positive-negative, in the embodiment, the upper ferromagnetic film of the two side skyrmion racetracks is ferromagnetic film a, the lower ferromagnetic film is ferromagnetic film b, the upper ferromagnetic film of the middle skyrmion racetrack 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 the embodiment, the material of the non-magnetic intermediate layer is non-magnetic metal ruthenium, the material of the ferromagnetic film a is magnetic metal cobalt, and the material of the ferromagnetic film b is magnetic metal cobalt-iron-boron. Figure 3 is a magnetic moment distribution diagram of the skyrmions in the ferromagnetic film b and the ferromagnetic film a in the middle skyrmion racetrack.

[0039] In the middle skyrmion racetrack, due to the skyrmion Hall effect, the skyrmions therein will move along the deflection direction of the lower right corner, as shown in Figure 4 (a) of FIG. 8, wherein the lower ferromagnetic film is ferromagnetic film a, i.e., magnetic metal cobalt, the upper ferromagnetic film is ferromagnetic film b, i.e., magnetic metal cobalt-iron-boron, and the arrow indicates the direction of the background magnetic moment (i.e., the peripheral magnetic moment of the skyrmion). In the two side skyrmion racetracks, due to the flipping of the magnetic film, the skyrmions therein will move along the direction of the upper right corner, as shown in Figure 4 (b) of FIG. 8, wherein the upper ferromagnetic film is ferromagnetic film a, i.e., magnetic metal cobalt, the lower ferromagnetic film is ferromagnetic film b, i.e., magnetic metal cobalt-iron-boron, and the arrow indicates the direction of the background magnetic moment (i.e., the peripheral magnetic moment of the skyrmion). That is, the skyrmions in adjacent racetracks deflect in opposite directions.

[0040] As Figure 5 shown, under the driving of the current, the skyrmions will first move to the right lower side due to the skyrmion Hall effect. Subsequently, at the boundary of the adjacent skyrmion racetrack (x = -25 nm), due to the opposite skyrmion Hall effect on the two sides, the skyrmions will first oscillate up and down along the boundary until the velocity in the x direction is offset, and finally move linearly along the boundary. At this time, the skyrmion Hall effect is completely offset, thereby achieving precise control of the skyrmions. y y

[0041] The skyrmions in the skyrmion racetrack memory are driven by spin-polarized current with different current densities, as shown in Figure 6 , wherein the abscissa is the current density of the driving current, and the ordinate is the speed of the skyrmion movement. It can be seen that the speed of the skyrmions and the size of the current density present a linear relationship. When the current density is 500 MA / cm 2 , the speed of the skyrmions can reach 580 m / s, which provides a good platform for high-speed processing of information. ​​

[0042] In addition, by optimizing the Gilbert damping of the material, the moving speed of the skyrmion can be further improved by using different preparation processes. As shown in Figure 7 , where the abscissa is the reciprocal of the Gilbert damping, and the ordinate is the speed of the skyrmion movement, it can be seen that the moving speed of the skyrmion is linearly related to the reciprocal of the Gilbert damping, that is, the smaller the Gilbert damping of the material, the faster the moving speed of the skyrmion.

[0043] In addition, as shown in Figure 8 , where the abscissa is the strength of the interlayer exchange coupling in the artificial ferrimagnet, and the ordinate is the speed of the skyrmion movement, the speed of the skyrmion is not very sensitive to the size of the interlayer RKKY interaction, and the size of the interlayer RKKY interaction is regulated by the thickness of the non-magnetic intermediate layer, which means that even if the thickness of the non-magnetic intermediate layer is not uniform, the speed of the skyrmion will not fluctuate obviously, which is of great significance to the stability of the skyrmion movement and the difficulty of reducing the material process. Embodiment 2

[0044] In this embodiment, the structure in Embodiment 1 is connected end to end to form a circular track memory, as shown in Figure 9 , where the inner radius of the circular ring is 100 nm, and the outer radius is 250 nm.

[0045] When a ring-shaped spin-polarized current along the clockwise direction is applied, since the moving direction of the electron is along the counterclockwise direction, the skyrmion will move along the counterclockwise direction, as shown in Figure 9 (a) of , it can be seen that the skyrmion will gradually deflect to the boundary of the coupled artificial ferrimagnet (a circle with a radius of 200 nm) due to the skyrmion Hall effect, and then, as in Embodiment 1, the skyrmion makes oscillatory motion in the radial direction perpendicular to the boundary, and then makes circular motion along the boundary.

[0046] When a ring-shaped spin-polarized current along the counterclockwise direction is applied, the skyrmion will move along the clockwise direction along the boundary of the coupled artificial ferrimagnet (a circle with a radius of 150 nm), as shown in Figure 9 (b) of . It can be seen that the present application can realize the movement of the skyrmion along the circular boundary, thereby regulating the direction of the speed of the skyrmion, which is of great significance to the precise control of the skyrmion in information storage.

[0047] The above examples only illustrate the principles of the present application and its efficacy, and are not intended to limit the application. Any modification or change on the above examples made by any person skilled in the art, without departing from the spirit and scope of the present application, shall be covered by the claims of the present application.

Claims

1. An artificial ferrimagnet-based skyrmion racetrack memory, characterized in that, The memory comprises a heavy metal layer, an artificial ferrimagnet layer and a read-write end arranged from bottom to top; The artificial ferrimagnet layer is composed of at least three parallel arranged SGM racetracks; The SGM racetrack comprises a lower ferromagnetic film, a non-magnetic intermediate layer and an upper ferromagnetic film arranged from bottom to top; the lower ferromagnetic film and the upper ferromagnetic film are magnetic materials with different saturation magnetization, and the non-magnetic intermediate layer provides RKKY interaction to realize the antiferromagnetic coupling between the upper and lower ferromagnetic films, thereby constructing an artificial ferrimagnet; meanwhile, the net magnetization of adjacent SGM racetracks is positive and negative, so that the SGMs in adjacent racetracks deflect in opposite directions, and the two opposite lateral displacements cancel each other out at the boundary, thereby enabling the magnetic SGMs to move along the boundary; The read-write end comprises a read end and a write end, wherein the write end is a magnetic tunnel junction located directly above the SGM racetrack, and the artificial ferrimagnetic SGMs are written by applying a pulse current; the read end is a magnetic tunnel junction located directly above the junction of the SGM racetrack, and the SGMs are read by measuring the magnetoresistance.

2. The artificial ferrimagnet-based skyrmion racetrack memory of claim 1, wherein, The materials of the lower ferromagnetic film and the upper ferromagnetic film are one of 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 material.

3. The artificial ferrimagnet-based skyrmion racetrack memory of claim 1, wherein, The material of the non-magnetic intermediate layer is a 4d / 5d non-magnetic transition metal.

4. The artificial ferrimagnet-based skyrmion racetrack memory of claim 1, wherein, The material of the heavy metal layer is platinum, iridium or tungsten.

5. A synthetic antiferromagnet-based skyrmion racetrack memory as claimed in any of claims 1-4, characterized in that, The width of the SGM racetrack ranges from 30 nm to 100 nm.

6. A synthetic antiferromagnet-based skyrmion racetrack memory as defined in claim 5, characterized in that, The thickness of the lower ferromagnetic film ranges from 1 nm to 10 nm; the thickness of the upper ferromagnetic film ranges from 1 nm to 10 nm; and the thickness of the non-magnetic intermediate layer ranges from 1 nm to 10 nm.

7. The artificial ferrimagnet-based skyrmion racetrack memory of claim 6, wherein, The shape of the SGM racetrack is linear, curved or ring-shaped.

8. The artificial ferrimagnet-based skyrmion racetrack memory of claim 7, wherein, The driving current of the SGM racetrack memory is changed to control the movement speed of the SGMs at the artificial ferrimagnetic boundary, thereby controlling the read-write speed of the SGM racetrack memory.

9. The artificial ferrimagnet-based skyrmion racetrack memory of claim 7, wherein, Different processing techniques are used to prepare the lower ferromagnetic film and the upper ferromagnetic film to control the Gilbert damping in the ferromagnetic film, thereby controlling the movement speed of the SGMs at the artificial ferrimagnetic boundary and further controlling the read-write speed of the SGM racetrack memory.

10. The artificial ferrimagnet-based skyrmion racetrack memory of claim 1, wherein, The heavy metal layer, the lower ferromagnetic film, the non-magnetic intermediate layer and the upper ferromagnetic film are prepared by magnetron sputtering, molecular beam epitaxy or pulsed laser deposition.

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