WO2024005274A1

WO2024005274A1 - Metal structure having magnetic domain wall formed and method for generating skyrmion

Info

Publication number: WO2024005274A1
Application number: PCT/KR2022/016724
Authority: WO
Inventors: 이기석; 한희성; 정대한; 김강휘; 정수영
Original assignee: 울산과학기술원
Priority date: 2022-06-28
Filing date: 2022-10-28
Publication date: 2024-01-04
Also published as: KR20240002077A

Abstract

The present invention relates to a metal structure that can be applied to a semiconductor device and, more specifically, to a metal structure or method for generating or controlling skyrmion present in a ferromagnetic material. A metal structure according to an embodiment of the present specification comprises: a heavy metal layer; and a ferromagnetic layer which is disposed on the heavy metal layer, includes a magnetic domain wall, and generates skyrmion on the basis of the movement of the magnetic domain wall.

Description

Metal structure with magnetic domain walls and skyrmion generation method

The present invention relates to a metal structure applicable to semiconductor devices, and more specifically, to a metal structure or method for generating or controlling skyrmions present in a ferromagnetic material.

As semiconductor integrated circuits become more highly integrated and perform better, new microfabrication technologies are continuously being developed. However, in conventional semiconductor devices, as the degree of integration increases, the gate oxide film no longer functions as an insulating film, and when the width of the wiring is reduced to increase the degree of integration, a short circuit in the wiring occurs. As such, in conventional semiconductor devices, there are structural limitations due to an increase in current density and there are limits to increasing integration.

Furthermore, as limitations such as thermal problems due to rapid increases in power consumption, stagnation in information processing speed, and rapid increases in manufacturing equipment and process costs are encountered, new concepts and approaches that break away from the existing silicon-based device concept are attempted. there is.

One example is research on skyrmion-based magnetic memory devices.

1 is a diagram schematically showing a conventional technique for performing information reading using skyrmions.

A skyrmion is a spin structure in the form of particles in which spins are arranged in a vortex-like spiral, and logic operations are performed by corresponding to digital codes in which the high level of the pulse voltage is set to 1 and the low level to 0 in the memory device. It can be designed to do so.

Specifically, referring to a in FIG. 1, the skyrmion (1) can serve as a basic unit (bit) of information storage, and through the movement of the skyrmion (1), the reader (3) as shown in b in FIG. The moment it passes, the value of the logic element bit can be read as 1 and function as a magnetic memory element.

However, skyrmions are generated only in some materials that exhibit a strong asymmetric exchange or Dzyaloshinskii-Moriya interaction (DMI) effect, and even if this DMI effect exists, there are technical limitations in generating skyrmions without controlling the physical properties or structure of the material. There is a downside to this.

Accordingly, we would like to provide a relatively simple structure and manufacturing method.

The embodiment of the present specification is proposed to solve the above-mentioned problems and proposes a metal structure with a magnetic domain wall for skyrmion generation and a skyrmion generation method.

The metal structure for achieving the above-described problem includes a heavy metal layer; and a ferromagnetic layer disposed on the heavy metal layer, including a magnetic domain wall, and generating skyrmions based on movement of the magnetic domain wall.

The ferromagnetic layer may form magnetization in a first direction in the first part and magnetization in the second direction in the second part.

The magnetic domain wall may have a moving speed greater than or equal to a threshold value.

A skyrmion generating device for achieving the above-described problem includes the metal structure; And it may include a magnetic field application unit. The skyrmion generating device includes the metal structure; And it may include a current applicator.

The method for generating the skyrmion to achieve the above-described problem includes generating a magnetic domain wall in the ferromagnetic layer; moving the magnetic domain wall included in the metal structure; And it may include generating a skyrmion based on the movement of the magnetic domain wall.

Creating a magnetic domain wall in the ferromagnetic layer may include forming magnetization in a first direction in a first portion of the ferromagnetic layer; It may include forming magnetization in a second direction in the second portion of the ferromagnetic layer. The step of generating a skyrmion based on the movement of the magnetic domain wall may include ensuring that the moving speed of the magnetic domain wall is greater than or equal to a threshold value.

The step of generating the skyrmion based on the movement of the magnetic domain wall includes moving the magnetic domain wall in a first direction to generate a skyrmion, and moving the magnetic domain wall in a second direction to generate the skyrmion. It may include moving in the second direction.

The step of moving the magnetic domain wall may include applying a magnetic field to the metal structure.

Applying the magnetic field to the metal structure may include applying the magnetic field in a vertical direction to the metal structure.

Applying the magnetic field to the metal structure includes applying the magnetic field as a pulse signal; And the step of generating skyrmions based on the movement of the magnetic domain wall may include controlling the number of skyrmions generated based on the pulse signal.

The step of moving the magnetic domain wall may include applying a current to the metal structure.

Applying the current to the metal structure may include applying the current to the metal structure in a horizontal direction.

Applying the current to the metal structure includes applying the current as a pulse signal; And the step of generating skyrmions based on the movement of the magnetic domain wall may include controlling the number of skyrmions generated based on the pulse signal.

According to an embodiment of the present invention, skyrmions can be generated using a relatively simple structure.

According to another embodiment of the present invention, the number of skyrmions generated can be controlled.

According to another embodiment of the present invention, the position of the skyrmion can be controlled.

Figure 2 is a diagram showing a metal structure for skyrmion generation.

Figures 3a and 3b are diagrams showing the main process in which a skyrmion generating device according to an embodiment of the present invention creates a magnetic domain wall in a metal structure and generates skyrmions.

Figures 4a and 4b are diagrams showing the main process in which the skyrmion generation device according to an embodiment of the present invention controls the number of generated skyrmions by applying a pulsed magnetic field to a metal structure.

Figure 5 is a flowchart showing a skyrmion generation method of the skyrmion generation device according to an embodiment of the present invention.

Figure 6 is a diagram showing the process by which the skyrmion generation device moves the magnetic domain wall and controls generation according to an embodiment of the present invention.

Figure 7 is a block diagram showing the block configuration of the skyrmion generation device of the present invention.

Since the present invention can be modified in various ways and can have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. The effects and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various forms.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. When describing with reference to the drawings, identical or corresponding components will be assigned the same reference numerals and redundant description thereof will be omitted. .

In the following embodiments, terms such as first and second are used not in a limiting sense but for the purpose of distinguishing one component from another component.

In the following examples, singular terms include plural terms unless the context clearly dictates otherwise.

In the following embodiments, terms such as include or have mean that the features or components described in the specification exist, and do not exclude in advance the possibility of adding one or more other features or components.

In the drawings, the sizes of components may be exaggerated or reduced for convenience of explanation. For example, the size and thickness of each component shown in the drawings are shown arbitrarily for convenience of explanation, so the present invention is not necessarily limited to what is shown.

In the following description of the present disclosure, if a detailed description of a related known function or configuration is determined to unnecessarily obscure the gist of the present disclosure, the detailed description will be omitted.

Figure 2 is a diagram showing a metal structure for skyrmion generation.

The metal structure for generating skyrmions in FIG. 2 consists of a heavy metal layer 23 and a ferromagnetic layer 21.

The ferromagnetic layer 21 is a material that is strongly magnetized in the direction of the magnetic field when a strong magnetic field is applied from the outside and then remains magnetized even when the external magnetic field disappears. Specifically, it is an alloy-based magnetic material such as CoFe, CoFeB, etc., or Co2FeSi with perpendicular anisotropy. Heusler alloy-based magnetic materials such as , Co2MnSi, etc. may be used.

Such a ferromagnetic layer 21 is formed into a single layer through processes such as sputtering, molecular beam epitaxy (MBE), atomic layer deposition (ALD), pulse laser deposition (PLD), and electron beam evaporator. As a (mono_layer) structure, it can be formed as a single layer for interfacial Dzyaloshinskii-Moriya interaction (DMI) or as a multilayer structure. In addition, when using the interface DMI, the ferromagnetic layer 21 has a single-layer structure, and its thickness may range from, for example, several Å to several nm, and its line width may range, for example, from several tens of nm to several μm. You can.

For the heavy metal layer 23, any one or a mixture of two or more of platinum, tantalum, iridium, tantalum, hafnium, tungsten, and palladium may be used, and processes such as sputtering, MBE, ALD, and PLD electron beam evaporator may be used as the heavy metal layer 23. It can be formed into a single-layer structure or a multi-layer structure. Here, the thickness of the heavy metal layer 23 may range from several nm to several tens of nm, for example, and its line width may range from several tens of nm to several μm, for example.

The metal structure of the present invention may have fewer limitations in physical properties than in the case where the conventional DMI action is strong, and as will be described later, skyrmions can be generated based on the movement of the magnetic domain walls.

Figures 3a and 3b are diagrams showing the main process in which the skyrmion generating device according to an embodiment of the present invention creates a magnetic domain wall in a metal structure and generates skyrmions. These metal structures can create magnetic domain walls in the ferromagnetic layer. Specifically, the ferromagnetic layer is divided into magnetization zones in various directions. This magnetization region is called a magnetic domain, and the boundary between the magnetic domains can be called a magnetic domain wall.

Referring to FIG. 3A, the metal structure may form magnetization in a first direction in the first part 31 of the ferromagnetic layer and magnetization in the second direction in the second part 33. For example, the direction of magnetization in the first direction of the first part 31 may be up, and the direction of magnetization in the second direction of the second part 33 may be down.

Such a ferromagnetic layer can generate a plurality of magnetic domains with different directions in the ferromagnetic material by applying an external magnetic field to form magnetization.

Accordingly, the first part 31 and the second part 33 each form a magnetic domain, and a magnetic domain wall 35 is created as a boundary of the magnetic domain.

When a magnetic field or current is applied in a specific direction while a magnetic domain wall is formed on the ferromagnetic layer, an effect such as the area of the specific magnetic domain being expanded and the magnetic domain wall 35 moving may occur.

Specifically, referring to FIG. 3B, when a magnetic field is applied in the first or up direction, the area of the magnetic domain of the first part 31 expands and the magnetic domain wall 35 moves. As a stronger magnetic field is applied, the magnetic domain wall 35 moves. )'s movement speed can become faster.

When the magnetic domain wall 35 exceeds a certain speed, a magnetic domain wall deformation phenomenon called walker breakdown occurs.

In the case of general ferromagnetic materials, after the Walker collapse phenomenon occurs, the magnetic domain walls are deformed and the speed of magnetic domain wall movement is limited.

However, if a stronger magnetic field is applied to a metal structure where DMI action may occur after the Walker collapse phenomenon occurs, skyrmions (1) may be generated in the magnetic domain wall (35).

As a result, the skyrmion 1 is formed by forming a magnetic domain wall 35, and can be generated by applying a magnetic field or current exceeding a threshold value to a metal structure in which DMI action can occur.

When a magnetic field or current exceeding a threshold value is applied to a metal structure, skyrmions 1 can be generated. Hereinafter, methods for controlling and controlling the number of skyrmions will be described later.

Figures 4a and 4b are diagrams showing the main process of controlling the number of skyrmions generated by applying a pulsed magnetic field to a metal structure according to an embodiment of the present invention. In particular, the magnetic domain wall in Figure 4b is moving within the metal structure, but is shown centered on the magnetic domain wall.

The number of skyrmions generated can be controlled by applying a pulsed magnetic field to a metal structure where a magnetic domain wall is formed and DMI action can occur. Specifically, when a magnetic field in which the maximum value of the pulse magnetic field is greater than the threshold value is applied to the metal structure in Figure 4a, the moving speed of the magnetic domain wall may vary depending on the direction and strength of the magnetic field, and skyrmions are formed around the magnetic domain wall as shown in Figure 4b. This may or may not be created. For example, the number of skyrmions can be limited by checking the generated skyrmions and limiting the number.

According to another embodiment of the present invention, when a current whose maximum value of the pulse current is greater than or equal to a threshold value is applied to the metal structure, the number of skyrmions generated can be controlled.

According to another embodiment of the present invention, the skyrmion is generated by applying a magnetic field above a threshold or a current above the threshold to the metal structure to move the magnetic domain wall in the first direction, and the skyrmion is generated by applying a magnetic field above the threshold to the metal structure. Alternatively, the magnetic domain wall may be moved in the second direction opposite to the first direction by applying a current below the threshold value. Through this method, the number of skyrmions can be controlled regardless of the length of the metal structure.

According to another embodiment of the present invention, the skyrmion is generated by moving the magnetic domain wall in the first direction by applying a unidirectional magnetic field greater than a threshold or a unidirectional current greater than the threshold to the metal structure, and the skyrmion is generated by moving the magnetic domain wall in the first direction. It can be generated by applying a magnetic field in the other direction greater than a threshold or a current in the other direction greater than the threshold to move the magnetic domain wall in a second direction opposite to the first direction. Through this method, the number of skyrmions can be controlled regardless of the length of the metal structure.

The skyrmion generating device may generate a magnetic domain wall in a ferromagnetic layer included in a metal structure including a heavy metal layer and a ferromagnetic layer in step S101. In step S101, the skyrmion generating device may generate a magnetic domain wall by forming magnetization in a first direction in the first part of the ferromagnetic layer and magnetization in the second direction in the second part of the ferromagnetic layer. For example, the skyrmion generating device may apply an up-directed magnetic field to the first part of the ferromagnetic layer, or apply a current to form up-directed magnetization to form up-directed magnetization in the first part. Additionally, the skyrmion generating device may apply a downward-directed magnetic field to the second part of the ferromagnetic layer, or apply a current to form downward-directed magnetization to form downward-directed magnetization in the second part.

The skyrmion generating device may move the magnetic domain wall included in the metal structure in step S103. Specifically, the skyrmion generating device can apply a magnetic field or current to move the magnetic domain wall included in the metal structure.

When the skyrmion generating device applies a magnetic field to the metal structure, the magnetic domain wall can be moved by applying the magnetic field in a vertical direction to the metal structure.

When the skyrmion generating device applies current to the metal structure, the magnetic domain wall can be moved by applying the current in the horizontal direction of the metal structure.

The skyrmion generating device may generate skyrmions based on the movement of the magnetic domain wall included in the metal structure in step S105. For example, the skyrmion generating device can generate skyrmions by ensuring that the moving speed of the magnetic domain wall within the metal structure is greater than or equal to a threshold value. Additionally, the skyrmion generating device can apply a magnetic field above a threshold or a current above a threshold to the metal structure and generate skyrmions at the magnetic domain wall.

The skyrmion generation device according to another embodiment of the present invention can control the number of skyrmions generated in step S105. When a magnetic field is applied to a metal structure as a pulse signal, the number of skyrmions generated can be controlled based on the pulse signal. Specifically, when the maximum intensity of the magnetic field of the pulse signal is greater than the threshold, the number of skyrmions generated can be controlled.

Additionally, when applying current to a metal structure as a pulse signal, the number of skyrmions generated can be controlled based on the pulse signal. Specifically, when the maximum intensity of the current of the pulse signal is greater than the threshold, the number of skyrmions generated can be controlled.

Figure 6 is a diagram showing the process by which the skyrmion generation device moves the magnetic domain wall and controls generation according to an embodiment of the present invention. FIG. 6 may correspond to S103 or S105 in FIG. 5.

In step S201, the skyrmion generating device may apply a magnetic field or current to a metal structure including a heavy metal layer and a ferromagnetic layer and having a magnetic domain wall formed thereon.

The skyrmion generating device may generate the first skyrmion by moving the magnetic domain wall in the first direction in step S203. Specifically, the skyrmion generating device may generate skyrmions by ensuring that the moving speed of the magnetic domain wall in the first direction within the metal structure is greater than or equal to a threshold value. Additionally, the skyrmion generating device can apply a magnetic field above a threshold or a current above a threshold to the metal structure and generate skyrmions at the magnetic domain wall.

In step S205, the skyrmion generating device may move the magnetic domain wall in a second direction opposite to the first direction to move the first skyrmion in the second direction. Specifically, the skyrmion generating device may move the first skyrmion generated in step S203 in the second direction by ensuring that the movement speed of the magnetic domain wall in the second direction within the metal structure is below a threshold value. Additionally, the skyrmion generating device may apply a magnetic field below a threshold value or a current below a threshold value to the metal structure and move the magnetic domain wall in the second direction.

The skyrmion generating device may generate a second skyrmion by moving in the first direction in step S207. Specifically, the skyrmion generating device may generate skyrmions by ensuring that the moving speed of the magnetic domain wall in the first direction within the metal structure is greater than or equal to a threshold value. Additionally, the skyrmion generating device can apply a magnetic field above a threshold or a current above a threshold to the metal structure and generate skyrmions at the magnetic domain wall.

The skyrmion generating device can generate skyrmions by moving the magnetic domain wall in a first direction, control the movement direction of the skyrmions by moving them in a second direction, and move the generated skyrmions to another metal structure. Afterwards, it can be moved again in the first direction to create a skyrmion and repeat the series of processes.

Furthermore, the skyrmion generating device according to another embodiment of the present invention may generate a second skyrmion by moving the magnetic domain wall in a second direction opposite to the first direction in step S205. Specifically, the skyrmion generating device may generate the second skyrmion by ensuring that the movement speed of the magnetic domain wall in the second direction within the metal structure is greater than or equal to a threshold value. Additionally, the skyrmion generating device can apply a magnetic field above a threshold or a current above a threshold to the metal structure and generate skyrmions at the magnetic domain wall.

Figure 7 is a block diagram showing the block configuration of the skyrmion generation device of the present invention. The skyrmion generating device 700 is shown as including a processor 710 and a skyrmion generating unit 720, but is not necessarily limited thereto. For example, the processor 710 and the skyrmion generator 720 may be physically independent components.

The processor 710 may be configured to generally control the skyrmion generating device 700. Specifically, the processor 710 may include a CPU, RAM, ROM, and a system bus. The processor 710 may be implemented as a single CPU or multiple CPUs (or DSP, SoC). In one embodiment, the processor 710 may be implemented as a digital signal processor (DSP), a microprocessor, or a time controller (TCON) that processes digital signals.

The skyrmion generation unit 720 may include a metal structure, a magnetic field application unit, and a current application unit. The metal structure includes a ferromagnetic layer and a heavy metal layer, so that DMI action can occur, a magnetic domain wall can be formed on the ferromagnetic layer, and skyrmions can be generated. The magnetic field applicator may apply a magnetic field to the metal structure to form a magnetic domain wall or move the magnetic domain wall. The current applicator may apply a current to the metal structure to form a magnetic domain wall or move the magnetic domain wall.

Meanwhile, in this specification and drawings, preferred embodiments of the present invention are posted, and although specific terms are used, they are used only in a general sense to easily explain the technical content of the present invention and aid understanding of the present invention. It is not intended to limit the scope of the invention. In addition to the embodiments disclosed herein, it is obvious to those skilled in the art that other modifications based on the technical idea of the present invention can be implemented.

Claims

Heavy metal layer; and

A metal structure disposed on a heavy metal layer, including a magnetic domain wall, and a ferromagnetic layer in which a skyrmion is generated based on movement of the magnetic domain wall.
According to claim 1,

A metal structure in which the ferromagnetic layer forms magnetization in a first direction in a first part and magnetization in a second direction in a second part.
According to clause 2,

The magnetic domain wall is a metal structure whose moving speed is greater than or equal to a threshold value.
According to claim 1,

The metal structure; and

A skyrmion generating device including a magnetic field application unit.
According to claim 1,

The metal structure; and

A skyrmion generating device including a current applicator.
In a method of generating skyrmions using a metal structure including a heavy metal layer and a ferromagnetic layer,

Creating a magnetic domain wall in the ferromagnetic layer;

moving the magnetic domain wall included in the metal structure; and

A method of generating a skyrmion including the step of generating a skyrmion based on movement of the magnetic domain wall.
According to clause 6,

The step of creating a magnetic domain wall in the ferromagnetic layer is,

forming magnetization in a first direction in a first portion of the ferromagnetic layer;

A method of generating skyrmions comprising forming magnetization in a second direction in a second portion of the ferromagnetic layer.
According to clause 6,

The step of generating a skyrmion based on the movement of the magnetic domain wall is,

A method of generating a skyrmion comprising ensuring that the moving speed of the magnetic domain wall is greater than or equal to a threshold value.
According to clause 6,

The step of generating the skyrmion based on the movement of the magnetic domain wall is,

Generate a skyrmion by moving the magnetic domain wall in a first direction,

A method of generating a skyrmion comprising moving the skyrmion in a second direction by moving the magnetic domain wall in a second direction.
According to clause 6,

The step of moving the magnetic domain wall is,

A method of generating skyrmions including the step of applying a magnetic field to the metal structure.
According to claim 10,

The step of applying the magnetic field to the metal structure,

A method of generating a skyrmion comprising applying the magnetic field in a vertical direction to the metal structure.
According to claim 10,

The step of applying the magnetic field to the metal structure,

applying the magnetic field as a pulse signal; and

The step of generating a skyrmion based on the movement of the magnetic domain wall is,

A method of generating skyrmions including the step of controlling the number of skyrmions generated based on the pulse signal.
According to clause 6,

The step of moving the magnetic domain wall is,

Method for generating skyrmions comprising applying a current to the metal structure
According to claim 13,

The step of applying the current to the metal structure is,

A method of generating a skyrmion comprising applying the current in a horizontal direction to the metal structure.
According to claim 13,

The step of applying the current to the metal structure is,

applying the current as a pulse signal; and

The step of generating a skyrmion based on the movement of the magnetic domain wall is,

A method of generating skyrmions including the step of controlling the number of skyrmions generated based on the pulse signal.