JP2021033579A - Arithmetic unit - Google Patents

Abstract

To provide an arithmetic unit capable of expressing a state indicating an arithmetic result by a positional relationship of a plurality of skyrmions moving in a circuit.SOLUTION: An arithmetic unit 1 includes a skyrmion circuit 10 formed, on a magnetic film 100, by patterning a circuit portion 11 where skyrmions S can exist and a non-circuit portion 12 where the skyrmions cannot exist, and a reading unit 20 that reads a state representing an arithmetic result based on a positional relationship between a plurality of skyrmions whose movement paths are restricted only to the circuit portion 11.SELECTED DRAWING: Figure 1

Description

The present invention relates to an arithmetic unit.

In recent years, it is known that skyrmions are produced in some substances having a chiral crystal structure (see, for example, Patent Documents 1 and 2). Skyrmions have a spiral electron spin structure with antiparallel magnetization at the center and parallel magnetization at the periphery with respect to the applied magnetic field.

Skyrmions have a very small diameter of several nm to several μm, so when applied to magnetic elements, the area for storing unit information can be made smaller than conventional technologies such as conventional magnetic bubble memory. it can.

Further, it is known that skyrmions can be driven by a minute electric field or current density, and are expected to be applied to high-density and low-power consumption magnetic storage, arithmetic elements, and the like.

Japanese Unexamined Patent Publication No. 2014-175417 International Publication No. 2016/158230

However, when the magnetic thin film in which skyrmions are generated is subjected to processing such as fine processing to change the shape of the magnetic thin film, the movement of the skyrmions is caused by the influence of the magnetic dipole generated depending on the shape. May be suppressed. Therefore, it is difficult to express the state showing the calculation result by the positional relationship of a plurality of skyrmions moving in the circuit, which is a problem for the realization of the calculation element.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an arithmetic unit capable of expressing a state showing an arithmetic result by the positional relationship of a plurality of skyrmions moving in a circuit.

The computing device according to one aspect of the present invention includes a skyrmion circuit formed by patterning a circuit portion in which skyrmions can exist and a non-circuit portion in which skyrmions cannot exist on a magnetic film. It is provided with a reading unit that reads a state representing a calculation result based on the positional relationship of a plurality of skyrmions whose movement paths are restricted only to the circuit portion.

According to the above aspect, it is possible to express a state in which the calculation result is shown by the positional relationship of a plurality of skyrmions moving in the circuit.

It is a schematic plan view which shows the structure of the arithmetic unit which concerns on this embodiment. It is explanatory drawing explaining an example of the state which shows the calculation result by skyrmion. It is a schematic cross-sectional view which shows the cross-sectional structure of a skyrmion circuit. It is explanatory drawing explaining the patterning method of a circuit part and a non-circuit part.

Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments thereof.
FIG. 1 is a schematic plan view showing the configuration of the arithmetic unit 1 according to the present embodiment. The arithmetic unit 1 according to the present embodiment includes a skyrmion circuit 10 and a reading unit 20 that reads a state representing an arithmetic result from the skyrmion circuit 10.

The skyrmion circuit 10 is formed by patterning a circuit portion 11 in which the skyrmion S can exist and a non-circuit portion 12 in which the skyrmion S cannot exist on the magnetic film 100.

The skyrmion S generated in the circuit portion 11 has a vector structure in which the solid angle occupied by the magnetization vector becomes 4π when the magnetization vectors are collected in a specific region, and the skyrmion S of one skyrmion S has a vector structure. When another skyrmion S is present in the vicinity, a magnetic interaction acts between the two. Further, it is known that each skyrmion S moves randomly (Brownian motion) under the influence of thermal fluctuation. As a result, the positions of the plurality of skyrmions S whose movement paths are restricted only to the circuit portion 11 are autonomously determined according to the movement of each skyrmion S due to thermal fluctuation and the interaction between the skyrmions S. ..

The circuit portion 11 has wiring patterns 11A to 11C for defining the movement path of the skyrmion S. The wiring patterns 11A to 11C are, for example, linear patterns having a width dimension of 1 to 2 μm and a length dimension of about 10 to 30 μm, and are formed substantially parallel to each other and at appropriate intervals. One or a plurality of skyrmions S are introduced into the wiring patterns 11A to 11C, respectively.

The skyrmion S introduced in the wiring patterns 11A and 11C has the wiring patterns 11A and 11C, respectively, due to the interaction from the skyrmion S introduced in the adjacent wiring pattern 11B and its own Brownian motion caused by the thermal fluctuation. It is possible to move on. Similarly, the skyrmion S introduced in the wiring pattern 11B has the wiring pattern 11B due to the interaction from the skyrmion S introduced in the adjacent wiring patterns 11A and 11C and its own Brownian motion caused by the thermal fluctuation. It is possible to move on.

As a result, the skyrmion S introduced in each wiring pattern 11A to 11C moves from the initial position to a more stable position due to the interaction from other skyrmions S and its own Brownian motion due to thermal fluctuation. Moving.

In the present embodiment, the configuration in which the circuit portion 11 has three wiring patterns 11A to 11C has been described, but the wiring pattern included in the circuit portion 11 is not limited to that shown in FIG. For example, the circuit portion 11 may be composed of one wiring pattern, or may be composed of two or four or more wiring patterns. Further, the wiring pattern constituting the circuit portion 11 does not have to be linear, and may be curved. Further, the circuit portion 11 may be a two-dimensional region having an appropriate area such as a rectangle or a circle, or a three-dimensional region having an appropriate volume such as a rectangular parallelepiped or a cube.

Further, in the example of FIG. 1, a state in which one skyrmion S is generated for each wiring pattern 11A to 11C is shown, but a plurality of skyrmions S may be generated for each wiring pattern 11A to 11C. In this case, one skyrmion S on the wiring pattern 11A interacts with another skyrmion S existing on the same wiring pattern 11A, and interacts with another skyrmion S existing on the other wiring patterns 11B and 11C. It is possible to move on the wiring pattern 11A by its own Brownian motion due to the action and thermal fluctuation. The same applies to the skyrmion S on the other wiring patterns 11B and 11C. Further, when the circuit portion 11 is composed of a two-dimensional region or a three-dimensional region, a plurality of skyrmions S may be generated in these regions.

The reading unit 20 includes one or a plurality of detection elements 21 for detecting the skyrmion S, and an arithmetic circuit (not shown) that performs various calculations based on the detection results of the detection elements 21. As the detection element 21, for example, a TMR element having a tunnel magneto-resistance effect (TMR) in which the electric resistance changes according to a magnetic field can be used. The detection element 21 is provided assuming a stable position of the skyrmion S. For example, as shown in FIG. 1, the detection element 21 is provided near both ends of the wiring patterns 11A to 11C. Further, the detection element 21 may be provided near the center of each wiring pattern 11A to 11C in the length direction. The detection element 21 detects the presence or absence of skyrmion S by measuring the change in electrical resistance according to the presence or absence of skyrmion S at the installation position. The reading unit 20 identifies the positional relationship of the skyrmion S based on the detection result by the detection element 21, and reads the state representing the calculation result.

In the present embodiment, the configuration in which the TMR element is used as the detection element 21 has been described, but the detection element 21 is not limited to the TMR element. For example, if the skyrmion S has a submicron size, it can be visually observed with a magnetic optical microscope. Therefore, the positional relationship of the skyrmion S may be specified based on the microscope image of the magnetic optical microscope.

FIG. 2 is an explanatory diagram illustrating an example of a state showing a calculation result by Skyrmion S. As described above, the skyrmion S introduced in each wiring pattern 11A to 11C has a more stable position from the initial position due to the interaction from other skyrmions S and its own Brownian motion due to thermal fluctuation. Move to each. In FIG. 2A, two skyrmions S introduced in the wiring patterns 11A and 11C move to one end side in the length direction (upper end side in FIG. 2A), and one skyrmion S introduced in the wiring pattern 11B is It shows a state of moving to the other end side (lower end side in FIG. 2A). FIG. 2A shows the case where the upper end of the wiring patterns 11A and 11C is input, the lower end of the wiring pattern 11B is the output, the state where the skyrmion S exists is "1", and the state where the skyrmion S does not exist is "0". The calculation result shows a state in which "1" is output with respect to the input of (1,1).

FIG. 2B shows a state in which the skyrmion S of the wiring pattern 11A has moved to the lower end side, the skyrmion S of the wiring pattern 11B has moved to the vicinity of the center, and the skyrmion S of the wiring pattern 11C has moved to the upper end side. .. FIG. 2B shows the case where the upper end of the wiring patterns 11A and 11C is input, the lower end of the wiring pattern 11B is the output, the state where the skyrmion S exists is "1", and the state where the skyrmion S does not exist is "0". The calculation result shows a state in which "0" is output with respect to the input of (0,1). The same applies to the state in which the skyrmion S of the wiring pattern 11A moves to the upper end side, the skyrmion S of the wiring pattern 11B moves to the vicinity of the center, and the skyrmion S of the wiring pattern 11C moves to the lower end side. Indicates a state in which "0" is output with respect to the input of 1,0).

FIG. 2C shows a state in which the skyrmions S of the wiring patterns 11A and C have moved to the lower end side, and the skyrmions S of the wiring pattern 11B have moved to the upper end side. FIG. 2C shows the case where the upper end of the wiring patterns 11A and 11C is input, the lower end of the wiring pattern 11B is the output, the state where the skyrmion S exists is "1", and the state where the skyrmion S does not exist is "0". The calculation result shows a state in which "0" is output with respect to the input of (0,0).

That is, the skyrmion circuit 10 shown in FIGS. 2A to 2C outputs "1" to the input of (1,1), and outputs (0,1) or (1,0) or (0,0). It shows that a logical product circuit that outputs "0" to the input is configured.

In the example of FIG. 2, the configuration of the logical product circuit using the skillmion S is shown, but other arithmetic circuits such as the logical sum, the negative logical product, and the exclusive OR are constructed by using the skillmion circuit 10. Alternatively, an arithmetic circuit such as a full adder may be constructed.

Further, the arithmetic unit 1 may be configured to include a voltage application terminal in order to control the behavior of the skyrmion S. For example, the voltage application terminal is brought close to the center of the wiring patterns 11A and 11C, and the skyrmion S introduced in the wiring patterns 11A and 11C moves to the upper end side or the lower end side of each wiring pattern 11A and 11C. A voltage may be applied through the application terminal.

Hereinafter, a method of forming the skyrmion circuit 10 will be described.
FIG. 3 is a schematic cross-sectional view showing the cross-sectional structure of the skyrmion circuit 10. The skyrmion circuit 10 includes a magnetic film 100 formed on the substrate 150 and a protective film 120 laminated on the magnetic film 100. The substrate 150 is, for example, a silicon substrate and has an appropriate thickness.

The magnetic film 100 has, for example, a laminated structure in which a non-magnetic base layer 101, a ferromagnetic layer 102, and a non-magnetic insertion layer 103 are laminated in this order.

The ferromagnetic layer 102 is formed of a material in which the magnetic moment is magnetized perpendicularly to the substrate surface due to magnetocrystalline anisotropy. As such a material, a material containing a magnetic metal element such as Fe, Co, Ni, a perovskite type oxide such as _{SrRuO 3 and the like are used.} In the present embodiment, as an example of the ferromagnetic layer 102, cobalt iron boron (CoFeB) is formed to a thickness of 1.25 nm. The thickness of the ferromagnetic layer 102 is appropriately determined according to the material within the range in which the skyrmion S can exist (or the condition of the boundary where the skyrmion S can be formed).

The non-magnetic base layer 101 is formed on the lower side of the ferromagnetic layer 102. The flatness of the film is improved by forming the non-magnetic base layer 101. The non-magnetic base layer 101 is formed of a material containing a non-magnetic metal element such as Ta, V, Cr, Ru, Pd, W, Au, and Pt. In the present embodiment, as an example, flatness is realized by forming a film of tantalum (Ta) to a thickness of 5 nm.

The non-magnetic insertion layer 103 has a strong spin-orbit interaction. The non-magnetic insertion layer 103 is formed of, for example, a material containing a non-magnetic metal element such as Ta, V, Cr, Ru, Pd, W, Au, and Pt. In the present embodiment, as an example of the non-magnetic insertion layer 103, tantalum is formed on the upper side of the ferromagnetic layer 102 to a thickness of 0.16 nm. Adjusting the spatial asymmetry of the ferromagnetic layer 102 by inserting the non-magnetic insertion layer 103 modulates the Jarosinsky-Moriya interaction near the interface. The Jarosinsky-Moriya interaction modulates the magnetization structure of the skyrmion S. When the ferromagnetic layer 102 is a thin film having about several atoms in the thickness direction, the Jarosinsky-Moriya interaction affects from the laminated interface to the surface of the ferromagnetic layer 102. Due to the Jarosinsky-Moriya interaction, the magnetic moment in the ferromagnetic layer 102 aligned in parallel becomes stable in a twisted state, and the skyrmion S stabilizes.

In the present embodiment, the configuration for stabilizing the skyrmion S by modulating the Jarosinsky-Moriya interaction has been described, but it is not limited to the Jarosinsky-Moriya interaction, and magnetic anisotropy and saturation magnetization have been described. , Skyrmion S may be stabilized by modulating parameters such as exchange interaction.

In the example of FIG. 3, the magnetic film 100 having a three-layer structure in which the non-magnetic base layer 101, the ferromagnetic layer 102, and the non-magnetic insertion layer 103 are laminated in this order is shown, but the magnetic film 100 has a three-layer structure. The structure is not limited, and may have a multilayer structure in which ferromagnetic layers and non-magnetic layers are alternately laminated.

The protective film 120 has, for example, a first protective film 121 in which magnesium oxide (MgO) is formed to a thickness of about 1.5 _{nm, and a second protective film 122 in which silicon dioxide (SiO 2} ) is formed to a thickness of about 3 nm. In the example of FIG. 3, the _{protective film 120 having the first protective film 121 made of MgO and the second protective film 122 made of SiO 2} is shown, but the configuration of the protective film 120 is limited to the example of FIG. It is not a thing and can be changed as appropriate according to the purpose of use.

The magnetic film 100 and the protective film 120 described above can be formed by using a magnetron sputtering apparatus. That is, the magnetic film 100 and the protective film 120 are formed by laminating the non-magnetic base layer 101, the ferromagnetic layer 102, the non-magnetic insertion layer 103, the first protective film 121, and the second protective film 122 on the silicon substrate in this order. Can be formed. As the film forming method, in addition to the magnetron sputtering method, a thin film forming method such as a thin film deposition method, a laser ablation method, or a molecular beam epitaxy method can be used.

FIG. 4 is an explanatory diagram illustrating a patterning method for the circuit portion 11 and the non-circuit portion 12. FIG. 4A shows a state in which the thickness of the protective film 120 is partially changed by further forming a film _{of SiO 2} in a specific region of the protective film 120. For example, a resist is applied on the second protective film 122, patterning is performed by electron beam lithography, and then the resist is partially removed, and SiO ₂ is vapor-deposited on the portion from which the resist has been removed by a sputtering device or the like. The thickness of the protective film 120 can be partially changed. The _{resist remaining after the vapor deposition of SiO 2} can be removed by ultrasonic cleaning or the like.

On the other hand, FIG. 4B shows a state in which the thickness of the protective film 120 is partially changed by removing a specific region of the protective film 120. For example, the resist is removed on the second protective film 122, the resist is partially removed after patterning by electron beam lithography, and a part of the second protective film 122 is scraped off by an Ar milling apparatus to protect the resist. The thickness of the film 120 can be partially changed. The resist remaining after the second protective film 122 is machined can be removed by ultrasonic cleaning or the like.

In this way, the thickness of the protective film 120 is partially changed by film formation or removal of the film, and the magnetic film 100 is distorted, thereby causing magnetic properties (magnetic anisotropy) in the two-dimensional plane of the magnetic film 100. Two regions with different sex, Jarosinsky-Moriya interaction, saturation magnetization, and exchange interaction) can occur.

In the present embodiment, the thickness of the protective film 120 is partially changed, and the magnetic characteristics of a part of the magnetic film 100 are changed, so that the magnetic film 100 is patterned with the circuit portion 11 and the non-circuit portion 12. Do. For example, when the magnetic film 100 is formed under the condition that the skyrmion S can be stably present, the thickness of the magnetic film 100 is changed so as to deviate from this condition, so that the region where the skyrmion S cannot exist ( The non-circuit portion 12) can be partially formed. On the contrary, when the magnetic film 100 is generated under the condition of the boundary where the skyrmion S can exist, the skyrmion S can exist and the skyrmion S propagates by changing the thickness of the magnetic film 100 and shifting the condition. The region (circuit portion 11) to be formed can be partially formed.

As described above, in the present embodiment, the skyrmion S can exist in the two-dimensional plane of the magnetic film 100 without changing the shape of the magnetic film 100 by processing such as fine processing, and the skyrmion S can exist. A circuit portion 11 through which S is propagated and a non-circuit portion 12 in which the skyrmion S cannot exist can be formed. As a result, the influence of the demagnetizing field generated by the magnetic dipole appearing on the edge of the two-dimensional shape of the magnetic film 100 can be suppressed, and the movement of the skyrmion S can be avoided from being suppressed.

In the present embodiment, in order to pattern the circuit portion 11 and the non-circuit portion 12 on the magnetic film 100, the thickness of the protective film 120 is partially changed to obtain the magnetic characteristics of a part of the magnetic film 100. The configuration was changed. Alternatively, the magnetic properties of the magnetic film 100 may be changed by doping the magnetic film 100 or the protective film 120 with ions. For example, when ions of a non-magnetic element such as Si are doped, the strength of the exchange interaction can be changed, so that the magnetic properties of the magnetic film 100 can be changed. Further, for example, when ions of heavy metal elements such as Ta, Ir, and Pt are doped, the strength of the Jarosinsky-Moriya interaction can be changed, so that the magnetic properties of the magnetic film 100 can be changed.

10 Skyrmion circuit 11 Circuit part 12 Non-circuit part 20 Reading part 21 Detection element 100 Magnetic film S Skyrmion

Claims (6)

A skyrmion circuit formed by patterning a circuit part where skyrmion can exist and a non-circuit part where skyrmion cannot exist on a magnetic film,
An arithmetic unit including a reading unit that reads a state representing an arithmetic result based on the positional relationship of a plurality of skyrmions whose movement paths are restricted only to the circuit portion. The arithmetic unit according to claim 1, wherein the position of each skyrmion is autonomously determined according to the movement of each skyrmion due to thermal fluctuation and the interaction between the skyrmions. The arithmetic unit according to claim 2, wherein the reading unit includes a skyrmion detecting element provided corresponding to a position of each skyrmion determined autonomously. The arithmetic unit according to any one of claims 1 to 3, wherein the skyrmion circuit includes a plurality of skyrmion movement paths composed of the circuit portion. The arithmetic unit according to claim 4, wherein the circuit portion is patterned so that an interaction between a skyrmion moving on one movement path and a skyrmion moving on another movement path works. Claim 1 in which the circuit portion and the non-circuit portion are patterned on the magnetic film by making the magnetic characteristics of the magnetic film in the circuit portion different from the magnetic characteristics of the magnetic film in the non-circuit portion. The computing device according to any one of claims 5.

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