A method for generating skyrmions based on graphene and metal composite materials

Abstract

The invention discloses a method for generating skyrmions based on a graphene and metal composite material, comprising the following steps: constructing a magnetic multilayer film structure and generating skyrmions; the invention adjusts the thickness between graphene and ferromagnetism to adjust the DMI value and the PMA value of the structure, and the DMI value of the composite material layer to achieve the generation of skyrmions in the magnetic structure; injects a spin polarized current into a current injection layer to generate skyrmions; the addition of graphene can achieve better regulation of the DMI value and the PMA value of the structure, and realizes the nucleation of various magnetic structures in a larger range; the graphene and ferromagnetism can induce a larger DMI, and the DMI no longer requires a non-magnetic layer to have a strong spin-orbit coupling, thereby greatly expanding the selection range of heterostructure materials; in addition, the addition of graphene can not only play an antioxidant role on the metal layer, but also be used as an active agent to facilitate the growth of the ferromagnetic layer to form a multilayer film structure, and the feasibility is stronger.

Description

Technical Field

[0001] The present invention relates to the technical field of skyrmions, and in particular to a method for generating skyrmions based on a graphene and metal composite material. Background Art

[0002] With the rapid development of modern electronic information technology, higher and higher requirements are placed on the storage density and energy consumption of magnetic information storage devices. The size of magnetic skyrmions with particle characteristics is nanometer-scale (10-100nm), which is a magnetic structure with topological protection. The spin arrangement of skyrmions overcomes the size limitations of traditional magnetic materials and can ensure the reliability of stored information. The topological magnetic domain structure of skyrmions allows current to interact with it to produce a topological Hall effect. The current density for driving skyrmions is 5 to 6 orders of magnitude lower than that for driving traditional magnetic domain walls. Therefore, skyrmions are widely considered to be an information carrier in non-volatile spin storage devices with the characteristics of high speed, high density, and low energy consumption. They are expected to be used in a new generation of high-density, low-energy magnetic storage and spin electronics devices.

[0003] Most traditional methods for generating magnetic skyrmions are complicated to operate, utilize spin-polarized current, have low controllability, a narrow range of material selection, do not have good antioxidant effects, and are not feasible. Therefore, the present invention proposes a method for generating skyrmions based on graphene and metal composite materials to solve the problems existing in the prior art. Summary of the invention

[0004] In view of the above problems, the purpose of the present invention is to propose a method for generating skyrmions based on graphene and metal composite materials. The method achieves the generation of skyrmions in a magnetic multilayer film structure by adjusting the DMI value and PMA value between graphene and ferromagnetism, as well as the DMI value of the composite material layer. Skyrmions are generated by injecting a spin-polarized current into a current injection layer, thereby improving the controllability, material selection range, antioxidant effect and feasibility of the method for generating skyrmions.

[0005] In order to achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a method for generating skyrmions based on a graphene and metal composite material, comprising the following steps:

[0006] Step 1: Constructing a magnetic multilayer film structure

[0007] Firstly, a composite material layer CoPt is arranged on the substrate layer, then a ferromagnetic layer Co is added on the composite material layer, then a graphene layer is arranged on the ferromagnetic layer, and finally a current injection layer is arranged on the graphene layer, and a complete calculation model is formed by the substrate layer, the composite material layer, the ferromagnetic layer, the graphene layer and the current injection layer, wherein the substrate layer, the composite material layer, the ferromagnetic layer, the graphene layer and the current injection layer are at the same geometric center;

[0008] Step 2: Producing skyrmions

[0009] According to step one, after the magnetic multilayer film structure is constructed, a spin-polarized current is injected into the current injection layer with an injection time of 0.5ns, and the PMA value between the graphene layer and the ferromagnetic layer and the DMI value between the ferromagnetic layer and the composite material layer are adjusted to finally generate skyrmions.

[0010] A further improvement is that in step one, the substrate layer, composite material layer, ferromagnetic layer, graphene layer and current injection layer are all disc structures, the radius of the substrate layer, composite material layer, ferromagnetic layer and graphene layer is 100nm, the radius of the current injection layer is 10nm, and the thickness of the ferromagnetic layer is 0.4nm.

[0011] A further improvement is that in step 1, the base layer is a magnesium oxide insulating base, the composite material layer is a ferromagnetic and heavy metal layer, and the heavy metal layer is a Pt layer.

[0012] A further improvement is that the ferromagnetic layer and the heavy metal interact to produce the DMI value required for stabilizing the magnetic skyrmions, and the graphene layer interacts with the ferromagnetic layer to form an adjustable DMI value and PMA value.

[0013] A further improvement is that in the step 2, after the current injection layer injects the spin polarized current, the ferromagnetic and heavy metals provide DM interaction due to the giant spin orbit coupling effect, and skyrmions are generated after the spin polarized current is injected.

[0014] A further improvement is that in step 2, after the current injection layer injects a spin-polarized current, the action of graphene causes a DMI value to be generated between the graphene layer and the ferromagnetic layer and increases the PMA value, and skyrmions are successfully generated after a spin-polarized current is injected through the current injection layer.

[0015] The beneficial effects of the present invention are as follows: the present invention changes the DMI value and the PMA value in the model and the DMI value of the composite material layer by adjusting the thickness between graphene and ferromagnetism to realize the generation of skyrmions in the magnetic structure, and generates skyrmions by injecting a spin-polarized current into the current injection layer; and by adding graphene, the DMI value and the PMA value of the structure are better regulated, and the nucleation of various magnetic structures is realized in a larger range, and graphene and ferromagnetism can induce a larger DMI, and the DMI no longer requires the non-magnetic layer to have a strong spin-orbit coupling, thereby greatly expanding the selection range of heterostructure materials; in addition, the addition of graphene can not only play an antioxidant role on the metal layer, but also be used as an active agent to facilitate the growth of the ferromagnetic layer, forming a multilayer film structure, and the feasibility is stronger. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0017] Figure 1 It is a schematic diagram of the magnetic structure of the present invention. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", "fourth", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0020] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] Embodiment 1

[0022] See also Figure 1 This embodiment provides a method for generating skyrmions based on a graphene and metal composite material, comprising the following steps:

[0023] Step 1: Constructing a magnetic multilayer film structure

[0024] First, a composite material layer CoPt is arranged on the substrate layer, and then a ferromagnetic layer Co is added on the composite material layer, and then a graphene layer is arranged on the ferromagnetic layer, and finally a current injection layer is arranged on the graphene layer, and a complete calculation model is formed by the substrate layer, the composite material layer, the ferromagnetic layer, the graphene layer and the current injection layer; the substrate layer, the composite material layer, the ferromagnetic layer, the graphene layer and the current injection layer are at the same geometric center, and the substrate layer, the composite material layer, the ferromagnetic layer, the graphene layer and the current injection layer are all disk structures; the radius of the substrate layer, the composite material layer, the ferromagnetic layer and the graphene layer is 100nm, the radius of the current injection layer is 10nm, and the thickness of the ferromagnetic layer is 0. .4nm, the substrate layer is a magnesium oxide insulating substrate, the composite material layer is a ferromagnetic and heavy metal layer, the heavy metal layer is a layer of Pt, the ferromagnetic and heavy metal interact to produce the DMI value required for stable magnetic skyrmions, the graphene layer interacts with the ferromagnetic layer to form an adjustable DMI value and PMA value, the DM interaction makes the adjacent magnetic moments perpendicular to each other, the existence of DMI breaks the spatial inversion symmetry of the spin system, for example, different DM interactions are generated by different strengths of spin-orbit coupling through heavy metals of different thicknesses, different DMI values ​​are obtained between the graphene and ferromagnetic layers due to different strengths of Rashba effects, and at the same time, the perpendicular magnetocrystalline anisotropy is improved;

[0025] Step 2: Producing skyrmions

[0026] According to step one, after the magnetic multilayer film structure is constructed, a spin-polarized current is injected into the current injection layer, the injection time is 0.5ns, and the PMA value between the graphene layer and the ferromagnetic layer and the DMI value of the ferromagnetic layer and the composite material layer are adjusted, and finally skyrmions are generated; after the current injection layer injects the spin-polarized current, the ferromagnetic and heavy metals provide DM interaction due to the giant spin-orbit coupling effect, and after the spin-polarized current is injected, skyrmions are generated; different from the nucleation of the magnetic structure in the Co / CoPt structure, it is a vortex state in which the nucleus and the center of the disk are not in the same position. The addition of graphene enables skyrmions to be successfully generated in the magnetic double-layer film. After the current injection layer injects the spin-polarized current, the action of graphene causes the DMI value to be generated between the graphene layer and the ferromagnetic layer and the PMA value to be increased, and skyrmions are successfully generated after the spin-polarized current is injected through the current injection layer.

[0027] Embodiment 2

[0028] See also Figure 1The magnetic structure includes a current injection layer, a graphene layer, a ferromagnetic layer, a ferromagnetic and heavy metal composite layer (the composite material is cobalt and platinum) and a substrate layer. Under the action of the current, skyrmions are generated in the center of the magnetic nanodisk, and the ferromagnetic and heavy metals interact to produce the DM (Dzyaloshinskii-Moriya) interaction value required for stabilizing the magnetic skyrmions, referred to as the DMI value; through exchange coupling, a ferromagnetic layer is coupled to the ferromagnetic and heavy metal composite layer; the graphene layer interacts with the ferromagnetic layer to form an adjustable DMI value and PMA (perpendicular magnetic anisotropy) value. The bottom of the magnetic structure is an insulating substrate, and a magnesium oxide substrate is selected. The entire magnetic structure forms a multilayer film disk model.

[0029] The generation of skyrmions in the magnetic structure is achieved by adjusting the DMI value and PMA value between the graphene layer and the ferromagnetic layer, as well as the DMI value of the composite material layer. Skyrmions are generated by injecting spin-polarized current into the current injection layer. The current injection time is 0.5ns, and the relaxation time is long enough.

[0030] Ferromagnetic and heavy metals provide DM interaction due to giant spin-orbit coupling; ferromagnetic layer and graphene will also cause a DMI value; both DMIs belong to interface effects, but the locations of their spin-orbit coupling energy are different; in the heavy metal cobalt / platinum structure, the DMI is the largest in the interface ferromagnetic layer, the cobalt layer, and its giant spin-orbit coupling energy comes from the heavy metal Pt layer; but in the graphene / ferromagnetic layer, the largest giant spin-orbit coupling energy and DMI come from the nearest neighbor ferromagnetic layer; the DMI value plays a great role in the generation of skyrmions, and the DMI value is a controllable parameter with multiple influencing factors; and the addition of graphene leads to an increase in the PMA value of the graphene / ferromagnetic layer, which means that skyrmions can be successfully generated in this structure.

[0031] Due to the exchange coupling, the magnetic moment structures of the upper and lower layers are the same; due to the difference in saturation magnetization, the magnetic moments are different in size; the skyrmions generated by this structure increase in radius as the DMI value increases, and 2π skyrmions appear, whose inner core also increases with the DMI.

[0032] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for generating skyrmions based on graphene and metal composite materials, characterized in that: The following steps are involved: Step 1: Constructing a magnetic multilayer film structure Firstly, a composite material layer CoPt is arranged on the substrate layer, and then a ferromagnetic layer Co is added on the composite material layer, and then a graphene layer is arranged on the ferromagnetic layer, and finally a current injection layer is arranged on the graphene layer, and a complete calculation model is formed by the substrate layer, the composite material layer, the ferromagnetic layer, the graphene layer and the current injection layer, wherein the substrate layer, the composite material layer, the ferromagnetic layer, the graphene layer and the current injection layer are at the same geometric center, the substrate layer is a magnesium oxide insulating substrate, the composite material layer is a ferromagnetic and heavy metal layer, and the heavy metal layer is a Pt layer; Step 2: Producing skyrmions According to step one, after the magnetic multilayer film structure is constructed, a spin-polarized current is injected into the current injection layer with an injection time of 0.5ns, and the PMA value between the graphene layer and the ferromagnetic layer and the DMI value between the ferromagnetic layer and the composite material layer are adjusted to finally generate skyrmions.

2. The method for generating skyrmions based on graphene and metal composite materials according to claim 1, characterized in that: In the step 1, the substrate layer, composite material layer, ferromagnetic layer, graphene layer and current injection layer are all disc structures, the radius of the substrate layer, composite material layer, ferromagnetic layer and graphene layer is 100nm, the radius of the current injection layer is 10nm, and the thickness of the ferromagnetic layer is 0.4nm.

3. The method for generating skyrmions based on graphene and metal composite materials according to claim 2, characterized in that: The ferromagnetic layer and the heavy metal interact to produce the DMI value required for stabilizing the magnetic skyrmions, and the graphene layer interacts with the ferromagnetic layer to form an adjustable DMI value and PMA value.

4. The method for generating skyrmions based on graphene and metal composite materials according to claim 1, characterized in that: In the step 2, after the current injection layer injects the spin polarized current, the ferromagnetic and heavy metal provide DM interaction due to the giant spin orbit coupling effect, and after the spin polarized current is injected, skyrmions are generated.

5. The method for generating skyrmions based on graphene and metal composite materials according to claim 1, characterized in that: In the step 2, after the current injection layer injects the spin-polarized current, the action of graphene causes the DMI value to be generated between the graphene layer and the ferromagnetic layer and increases the PMA value, and skyrmions are successfully generated after the spin-polarized current is injected through the current injection layer.

Images