Electrical device and memory element

Abstract

To provide an electrical device that utilizes the characteristics of a thin magnetic film in which skyrmions exist when an alternating current is passed through it.SOLUTION: An electrical device operates as at least one of an inductor and a capacitor, and includes a magnetic thin film in which at least a skyrmion crystal phase in which skyrmions are generated and a ferromagnetic phase are expressed in response to an applied magnetic field, and a pair of first electrodes connected to the magnetic thin film and passing an AC application current in a first direction on a main surface of the magnetic thin film in response to an AC application signal applied to the inductor or the capacitor, the pair of first electrodes functions as two terminals of the inductor or the capacitor.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an electric device and a memory element using skyrmions.

Background Art

[0002] Conventionally, skyrmion memories using magnetic elements capable of generating and erasing skyrmions have been known (for example, Patent Documents 1 to 4). [Patent Document 1] International Publication No. 2016 / 035758 [Patent Document 2] International Publication No. 2016 / 035579 [Patent Document 3] International Publication No. 2016 / 021349 [Patent Document 4] International Publication No. 2016 / 067744

Summary of the Invention

Problems to be Solved by the Invention

[0003] Provided are an electric device and a memory element that utilize the characteristics when an alternating current is passed through a magnetic thin film in which skyrmions exist.

Means for Solving the Problems

[0004] In a first aspect of the present invention, an electric device that operates as at least one of an inductor and a capacitor is provided. The electric device may include a magnetic thin film in which at least a skyrmion crystal phase and a ferromagnetic phase in which skyrmions are generated appear in response to an applied magnetic field. Any of the electric devices may include a pair of first electrodes connected to the magnetic thin film and flowing an alternating applied current corresponding to an alternating applied signal applied to the inductor or the capacitor in a first direction on a main surface of the magnetic thin film. In any of the electric devices, the pair of first electrodes may function as two terminals of the inductor or the capacitor.

[0005] In any of the above electrical devices, the first direction may be the longitudinal direction of the main surface of the magnetic thin film. In any of the above electrical devices, the electrical device may operate as the inductor.

[0006] In any of the above electrical devices, the first direction may be the short-side direction of the main surface of the magnetic thin film. In any of the above electrical devices, the electrical device may operate as the capacitor.

[0007] Any of the above electrical devices may be connected to the magnetic thin film and include a pair of second electrodes that pass the applied current in a second direction different from the first direction on the main surface of the magnetic thin film. In any of the above electrical devices, a control unit may be provided to control which of the pair of first electrodes and the pair of second electrodes the applied current is passed through according to whether the electrical device operates as either the inductor or the capacitor.

[0008] In any of the above electrical devices, the length of the main surface of the magnetic thin film in the first direction may be longer than the length of the main surface of the magnetic thin film in the second direction. In any of the above electrical devices, when the control unit operates the electrical device as the inductor, the applied current may be passed in the first direction, and when the control unit operates the electrical device as the capacitor, the applied current may be passed in the second direction.

[0009] In any of the above electrical devices, the length of the magnetic thin film in the first direction may be 5 times or more the diameter of the skyrmion.

[0010] In any of the above electrical devices, the length of the magnetic thin film in the second direction may be 1 time or more the diameter of the skyrmion.

[0011] In any of the above electrical devices, the length of the magnetic thin film in the second direction may be 2 times or less the diameter of the skyrmion.

[0012] Any of the above electrical devices may include a skyrmion generation unit that locally applies a magnetic field to the magnetic thin film to generate the skyrmions in the magnetic thin film.

[0013] In any of the above electrical devices, the first direction may be the longitudinal direction of the main surface of the magnetic thin film. Any of the above electrical devices may include a position adjustment unit that adjusts the position of the skyrmions in the first direction by flowing a direct current in the first direction.

[0014] Any of the above electrical devices may include a control unit that generates a plurality of skyrmions arranged in the first direction of the magnetic thin film by repeating the generation of the skyrmions by the skyrmion generation unit and the movement of the skyrmions by the position adjustment unit.

[0015] In any of the above electrical devices, the control unit may control the skyrmion generation unit and the position adjustment unit so that the distance between the skyrmions arranged in the first direction is equal to or greater than twice the diameter of the skyrmions.

[0016] In any of the above electrical devices, the control unit may control the number of skyrmions arranged in the first direction based on the inductance value or capacitance value that the electrical device should have.

[0017] In a second aspect of the present invention, a memory element that stores information depending on the presence or absence of skyrmions is provided. The memory element may include a magnetic thin film in which at least a skyrmion crystal phase and a ferromagnetic phase in which the skyrmions are generated in response to an applied magnetic field are exhibited. Any of the above memory elements may include a pair of first electrodes connected to the magnetic thin film and configured to flow a current in a first direction on a main surface of the magnetic thin film. Any of the above memory elements may include a current application unit that applies an alternating current to the first electrodes. Any of the above memory elements may include a detection unit that detects a phase difference between an emergent electric field generated when the alternating current flows and the alternating current, and detects the presence or absence of the skyrmions based on the phase difference.

[0018] Note that the above summary of the invention does not enumerate all features of the present invention. Also, sub-combinations of these feature groups can also be inventions.

Brief Description of the Drawings

[0019]

Figure 1

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Figure 20

Mode for Carrying Out the Invention

[0020] Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential for the solution means of the invention.

[0021] As an example of a magnetic material capable of forming skyrmions, there is a chiral magnetic material. A chiral magnetic material is a magnetic material in which the magnetic moment arrangement in the absence of an externally applied magnetic field becomes a magnetic order phase (helical magnetic phase) that rotates helically with respect to the traveling direction of the magnetic moment. By applying an external magnetic field, the chiral magnetic material becomes a ferromagnetic phase through a crystal phase in which skyrmions are arranged in a lattice.

[0022] FIG. 1 is a schematic diagram showing an example of a skyrmion 40 which is a nanostructured magnetic body in a magnetic thin film 11. In FIG. 1, each arrow indicates the direction of the magnetic moment in the skyrmion 40. The x-axis and the y-axis are axes orthogonal to each other, and the z-axis is an axis orthogonal to the xy plane.

[0023] The magnetic thin film 11 has a plane parallel to the xy plane. Magnetic moments oriented in all directions arranged in the magnetic thin film 11 constitute the skyrmion 40. In this example, the direction of the magnetic field applied to the magnetic thin film 11 is the plus z direction. In this case, the outermost magnetic moment of the skyrmion 40 of this example points in the plus z direction. In this example, the outermost circumference refers to the circumference of the magnetic moment that points in the same direction as the externally applied magnetic field shown in FIG. 1.

[0024] In the skyrmion 40, the magnetic moments are arranged so as to rotate in a spiral shape from the outermost circumference toward the inside. Further, the direction of the magnetic moment gradually changes from the plus z direction to the minus z direction toward the center of the vortex as the spiral rotation progresses. The skyrmion 40 is a nanostructured magnetic body having a spiral structure of magnetic moments. Once generated, the skyrmion 40 exists stably. Note that the skyrmion 40 can be erased by passing a relatively large current through the magnetic thin film 11 and causing it to collide with the end of the magnetic thin film 11.

[0025] When the magnetic thin film 11 in which the skyrmion 40 exists is a thin plate-like solid material, the magnetic moments constituting the skyrmion 40 are composed of the same magnetic moment in the z direction. That is, the skyrmion 40 has a magnetic structure composed of magnetic moments in the same direction from the front surface to the back surface in the depth direction (z direction) of the closed-path-shaped magnetic thin film 11. The magnetic thin film 11 is CoZn, MnSi, FeGe, MnGe, Cu2OSeO3, Co-Zn-Mn, Fe 2-x M x It may contain either Mo3N or GaV4S8. When the magnetic thin film 11 is CoZn, the skyrmion 40 can be generated and maintained from low temperature to about 187°C.

[0026] FIG. 2 is a schematic diagram showing skyrmions 40 with different helicities γ (i.e., the way of twisting of the magnetic moments). In particular, an example in the case where the skyrmion number Nsk = -1 is shown in (A) to (D) of FIG. 2. The skyrmion 40 in the case where the skyrmion number Nsk = -1 has a magnetic moment in the -z direction at its central part.

[0027] (E) of FIG. 2 shows the way of taking the coordinates of the magnetic moment (right-handed system). Since it is a right-handed system, the n x axis and the n y axis, the n z axis is taken in the direction from the back to the front of the paper surface. Also, the relationship between the shading and the direction of the magnetic moment is shown in (E) of FIG. 2.

[0028] The skyrmion number Nsk characterizes the skyrmion 40 which is a nanoscale magnetic structure having a spiral structure. The following [Equation 1] and [Equation 2] express the skyrmion number Nsk. In [Equation 2], the polar angle θ(r) between the magnetic moment and the z-axis is a continuous function of the distance r from the center of the skyrmion 40. The polar angle θ(r) changes from π to zero or from zero to π when r is changed from 0 to ∞.

[0029]

Equation

Equation

[0030] In [Equation 2], m is the vorticity and γ is the helicity. From [Equation 1] and [Equation 2], when θ(r) changes from r = 0 to ∞ and from π to zero, Nsk = -m.

[0031] FIG. 2 is a schematic diagram showing skyrmions 40 with different helicities γ. In particular, an example in the case of the skyrmion number Nsk = -1 is shown in FIGS. 2(A) to 2(D). FIG. 2(E) shows the way of taking the coordinates of the magnetic moment (right-handed system). Since it is a right-handed system, the n x axis and the n y axis, the n z axis is taken in the direction from the back to the front of the paper surface. Also, the relationship between the shading and the direction of the magnetic moment is shown in FIG. 2(E).

[0032] In FIGS. 2(A) to 2(D), the shading indicates the direction of the magnetic moment. Each arrow in FIGS. 2(A) to 2(D) indicates the magnetic moment separated by a predetermined distance from the center of the skyrmion 40. The magnetic structures shown in FIGS. 2(A) to 2(D) are in the state defining the skyrmion 40. The region with the lightest shading, like the outermost periphery in FIGS. 2(A) to 2(D), indicates the magnetic moment in the direction from the back surface to the front of the paper surface. In the figure, the said magnetic moment is represented in white. The region with the darkest shading, like the center in FIGS. 2(A) to 2(D), indicates the magnetic moment in the direction from the front to the back of the paper surface.

[0033] For each magnetic moment in FIG. 2(A) (γ = 0), the direction of each magnetic moment in FIG. 2(B) (γ = π) is the direction obtained by rotating each magnetic moment in FIG. 2(A) by 180°. For each magnetic moment in FIG. 2(A) (γ = 0), the direction of each magnetic moment in FIG. 2(C) (γ = -π / 2) is the direction obtained by rotating each magnetic moment in FIG. 2(A) by -90 degrees (90 degrees clockwise).

[0034] For each magnetic moment in (A) (γ = 0) of FIG. 2, the direction of each magnetic moment in (D) (γ = π / 2) of FIG. 2 is the direction obtained by rotating each magnetic moment in (A) of FIG. 2 by 90 degrees (90 degrees counterclockwise). Note that the skyrmion 40 with helicity γ = π / 2 shown in (D) of FIG. 2 corresponds to the skyrmion 40 in FIG. 1.

[0035] The four examples of magnetic structures illustrated from (A) to (D) in FIG. 2 may seem different, but they are topologically the same magnetic structure. The skyrmion 40 having the structures from (A) to (D) in FIG. 2, once generated, exists stably.

[0036] FIG. 3 is a phase diagram showing the magnetic field dependence of the magnetic body magnetic phase. The chiral magnetic body is a magnetic thin film in which the chiral magnetic phase changes to the skyrmion crystal phase (SkX) due to the magnetic field strength Bsk, and further changes to the ferromagnetic phase from the skyrmion crystal phase (SkX) at a stronger magnetic field strength Bf. In the skyrmion crystal phase (SkX), a plurality of skyrmions 40 are aligned in the closest-packed structure and generated in the xy plane.

[0037] Next, taking the magnitude of the magnetic exchange interaction of this magnetic thin film as J, various physical quantities are described by values standardized by this quantity. In this case, in the chiral phase having a helical magnetic moment magnetic structure at a low magnetic field, it changes to the skyrmion crystal phase at a magnetic field strength Bsk = 0.0075J. The diameter λ of the skyrmion 40 can be expressed as λ = 2π√2·J×a / D. Here, a is the lattice constant of the magnetic thin film 11, and D is the magnitude of the Dzyaloshinskii - Moriya interaction, which is a material - specific physical constant. Therefore, the skyrmion diameter λ is a material - specific constant. The skyrmion diameter λ is about 1 nm to 100 nm. For example, when the magnetic thin film 11 is FeGe, the skyrmion diameter λ is 70 nm, and when it is MnSi, it is 18 nm.

[0038] FIG. 4 is a perspective view showing an example of an electric device 100 according to the first embodiment of the present invention. The electric device 100 operates as at least one of an inductor and a capacitor using a skyrmion 40. The electric device 100 has a magnetic thin film 11 and a pair of first electrodes 12. In FIG. 4, the first electrode 12-1 and the first electrode 12-2 are shown as the pair of first electrodes 12. The electric device 100 may further include a magnetic field applying unit that applies a magnetic field to the magnetic thin film 11 to generate a skyrmion 40 in the magnetic thin film 11.

[0039] The pair of first electrodes 12 function as two terminals of an inductor or a capacitor. The pair of first electrodes 12 are connected to a circuit in which the electric device 100 is mounted. For example, the pair of first electrodes 12 are connected to the wiring of the circuit. The electric device 100 functions as an inductor or a capacitor in the circuit. An alternating applied signal that transmits through the circuit is applied to the first electrode 12.

[0040] As described in FIG. 3, in the magnetic thin film 11, at least a skyrmion crystal phase (SkX) where skyrmions are generated and a ferromagnetic phase appear according to the applied magnetic field. In the magnetic thin film 11 of FIG. 4, a skyrmion 40 already exists. The electric device 100 operates as an inductor or a capacitor with respect to the alternating applied signal by passing an alternating applied current corresponding to the applied signal through the magnetic thin film 11 in which the skyrmion 40 exists.

[0041] The pair of first electrodes 12 are connected to the magnetic thin film 11. The pair of first electrodes 12 pass an applied current corresponding to the applied signal in a first direction on the main surface of the magnetic thin film 11. The first direction may be the short side direction of the main surface of the magnetic thin film 11, the long side direction, or another direction. In this specification, when simply referred to as the "short side direction" or the "long side direction", it refers to the short side direction or the long side direction of the main surface of the magnetic thin film 11.

[0042] The longitudinal direction and the lateral direction may be perpendicular to each other. The length of the magnetic thin film 11 in the longitudinal direction is greater than the length of the magnetic thin film 11 in the lateral direction. The direction in which the length of the magnetic thin film 11 is minimized may be defined as the lateral direction. The direction in which the length of the magnetic thin film 11 is maximized may be defined as the longitudinal direction. When the main surface of the magnetic thin film 11 is rectangular, the direction parallel to the shortest side among the sides surrounding the main surface of the magnetic thin film 11 is defined as the lateral direction. Also, the direction parallel to the longest side among the sides surrounding the main surface of the magnetic thin film 11 is defined as the longitudinal direction. The magnetic thin film 11 may have a shape in which the corners of the rectangle are chamfered or rounded. In this case, the longitudinal direction and the lateral direction are the same as those of a rectangle whose corners are not chamfered or rounded. When the main surface of the magnetic thin film 11 is elliptical or oblong, the minor axis direction of the main surface of the magnetic thin film 11 is defined as the lateral direction, and the major axis direction is defined as the longitudinal direction.

[0043] In the example of FIG. 4, the first direction is the lateral direction (x-axis direction) of the main surface of the magnetic thin film 11. In this example, the pair of first electrodes 12 are arranged with the magnetic thin film 11 interposed therebetween in the lateral direction. In this case, the electric device 100 operates as a capacitor.

[0044] FIG. 5 is a diagram showing the movement of the skyrmion 40 in response to an applied alternating current. In FIG. 5, the positions of the skyrmion 40 at timings of t = 0, T / 4, T / 2, 3T / 4, and T are shown, where T is the period of the applied signal and the applied current. In this example, the direction of the applied current is reversed at timings t = 0, T / 2, and T. The frequency of the applied current in this example is 50 MHz.

[0045] When an applied current flows in the lateral direction of the magnetic thin film 11, the skyrmion 40 tries to move in the lateral direction. However, when the skyrmion 40 approaches the end side of the magnetic thin film 11, a repulsive force is generated between the end side and the skyrmion 40, and the movement of the skyrmion 40 in the lateral direction is suppressed. As a result, as shown in the figure from t = 0 to t = T / 2, the skyrmion 40 moves in the y-axis direction along the end side (the long side in this example).

[0046] When the direction of the applied current is reversed at the timing of t = T / 2, the moving direction of the skyrmion 40 is also reversed. As a result, the skyrmion 40 vibrates along the y-axis direction in response to the alternating applied current. The skyrmion 40 generates an emergent magnetic field. When the skyrmion 40 vibrates, the emergent magnetic field fluctuates periodically. Therefore, a periodic electric field (referred to as an emergent electric field) is generated as the skyrmion 40 moves.

[0047] Let the width in the short side direction of the magnetic thin film 11 be W, and the length in the long side direction be H. The width W is not less than 1 times the diameter λ of the skyrmion 40. Thereby, the skyrmion 40 can be generated in the magnetic thin film 11. The width W may be not more than 2 times the diameter λ of the skyrmion 40. By restricting the width W, when an applied current is passed in the short side direction, the movement of the skyrmion 40 in the short side direction can be suppressed. The width W may be not more than 1.5 times the diameter λ of the skyrmion 40.

[0048] Let the range in which the skyrmion 40 vibrates in the y-axis direction in response to the alternating applied current be YC. The range YC is determined according to the applied signal, the frequency, and the amplitude of the applied current. The range YC tends to be wider as the amplitude of the applied signal and the applied current is larger, and wider as the frequency is lower. Let the distance in the y-axis direction (long side direction) between the range YC and the side edge of the magnetic thin film 11 be Yd1. When the distance between one end of the range YC and the side edge of the magnetic thin film 11 is different from the distance between the other end of the range YC and the side edge of the magnetic thin film 11, the shorter of the two distances is taken as Yd1. The distance Yd1 is preferably not less than 2 times the diameter λ of the skyrmion 40. Thereby, the generation of the repulsive force in the Y-axis direction between the skyrmion 40 and the side edge of the magnetic thin film 11 can be suppressed. Therefore, it becomes easier to move the skyrmion 40 in the y-axis direction.

[0049] The length H of the magnetic thin film 11 is preferably designed such that the distance Yd1 is at least twice the diameter λ of the skyrmion 40. The length H may be five times or more, seven times or more, or even ten times or more the diameter λ of the skyrmion 40. The length H may be fifty times or less, thirty times or less, or even twenty times or less the diameter λ of the skyrmion 40. In the circuit in which the electric device 100 is implemented, when the ranges of the frequency and amplitude of the applied signal are determined, it is preferable to design the length H according to the frequency and amplitude. Also, at least one of the frequency and amplitude of the applied signal may be restricted according to the length H of the magnetic thin film 11 so as to ensure the distance Yd1.

[0050] FIG. 6 is a diagram showing an example of the current density of the applied current and the time waveform of the emergent electric field. FIG. 6 shows the current density and the emergent electric field of the example described in FIGS. 4 and 5. As described in FIGS. 4 and 5, in this example, an alternating applied current flows along the short side direction of the magnetic thin film 11. Also, a periodic emergent electric field is generated as the skyrmion 40 moves. The waveform of the emergent electric field corresponds to the voltage waveform applied between the pair of first electrodes 12.

[0051] As shown in FIG. 6, it can be seen that the phase of the emergent electric field is advanced by a phase difference Δ1 from the phase of the current density. That is, the electric device 100 functions as an element having a capacitance component with respect to the alternating applied signal. In this specification, an element having a capacitance component is referred to as a capacitor. The electric device 100 may function as an element combining a capacitance component and a resistance component. The closer the phase advance of the emergent electric field approaches 90 degrees, the more the electric device 100 operates as a pure capacitor.

[0052] As shown in FIG. 6, by flowing an applied current corresponding to the applied signal in the short side direction of the magnetic thin film 11, the electric device 100 can be made to function as a capacitor. Since the magnetic thin film 11 only needs to have a size corresponding to the diameter λ of the skyrmion 40, a small capacitor can be easily realized.

[0053] In this example, the distance Yd1 is equal to or greater than twice the diameter λ of the skyrmion 40. Thereby, the repulsive force received by the skyrmion 40 from the end side of the magnetic thin film 11 in the y-axis direction can be reduced. For this reason, the waveform of the emergent electric field shows a sine wave waveform similar to the applied current with almost no influence of the repulsive force.

[0054] FIG. 7 is a diagram showing the movement of the skyrmion 40 when the distance Yd1 is less than twice the diameter λ of the skyrmion 40. In FIG. 7, taking the periods of the applied signal and the applied current as T, the positions of the skyrmion 40 at each timing of t = 0, T / 8, T / 4, 3T / 8, T / 2, 5T / 8, 3T / 4, 7T / 8, T are shown. Also in this example, an applied current with the same current density as in the example of FIG. 5 flows in the short side direction of the magnetic thin film 11. In this example, the direction of the applied current is reversed at timings t = 0, T / 2, and T.

[0055] In the example of FIG. 7, the movement of the skyrmion 40 in the y-axis direction is suppressed as the skyrmion 40 approaches the end of the range YC. This is presumably because the distance Yd1 is small and the skyrmion 40 is easily subjected to a repulsive force in the y-axis direction from the end side of the magnetic thin film 11.

[0056] FIG. 8 is a diagram showing the current density of the applied current and the time waveform of the emergent electric field in the example of FIG. 7. Also in this example, the waveform of the emergent electric field is advanced in phase compared to the waveform of the current density. However, the waveform of the emergent electric field is greatly distorted. This is presumably because, as explained in FIG. 7, the movement of the skyrmion 40 in the y-axis direction is suppressed in the vicinity of the end of the range YC. For this reason, it is preferable that the distance Yd1 is equal to or greater than twice the diameter λ of the skyrmion 40.

[0057] FIG. 9 is a perspective view showing another example of the electric device 100. The electric device 100 in this example operates as an inductor using the skyrmion 40. A pair of first electrodes 12 in this example are arranged with the magnetic thin film 11 interposed therebetween in the longitudinal direction. In this case, the first direction in which the applied current flows is the longitudinal direction (y-axis direction) of the magnetic thin film 11.

[0058] FIG. 10 is a diagram showing the movement of the skyrmion 40 in response to an alternating applied current. FIG. 10 shows the movement of the skyrmion 40 in the example shown in FIG. 9. In FIG. 10, taking the period of the applied signal and the applied current as T, the positions of the skyrmion 40 at each timing of t = 0, T / 4, T / 2, 3T / 4, and T are shown. In this example, the direction of the applied current is reversed at the timings t = 0, T / 2, and T.

[0059] When an applied current flows in the longitudinal direction of the magnetic thin film 11, the skyrmion 40 moves in the longitudinal direction. When the direction of the applied current is reversed at the timing of t = T / 2, the moving direction of the skyrmion 40 is also reversed. As a result, the skyrmion 40 vibrates along the y-axis direction in response to the alternating applied current. The skyrmion 40 generates a spontaneous magnetic field. When the skyrmion 40 vibrates, the spontaneous magnetic field fluctuates periodically. For this reason, a periodic spontaneous electric field is generated as the skyrmion 40 moves.

[0060] In this example, the width W in the short-side direction of the magnetic thin film 11 is the same as that in the examples of FIGS. 4 to 6. The length H in the longitudinal direction of the magnetic thin film 11 may also be the same as that in the examples of FIGS. 4 to 6.

[0061] Let YL be the range in which the skyrmion 40 vibrates in the y-axis direction in response to the applied alternating current. The range YL is determined according to the frequency and amplitude of the applied signal and the applied current. The range YL may be different from the range YC. The range YL tends to become wider as the amplitude of the applied signal and the applied current increases, and tends to become wider as the frequency decreases. Let Yd2 be the distance in the y-axis direction (longitudinal direction) between the range YL and the edge of the magnetic thin film 11. When the distance between one end of the range YL and the edge of the magnetic thin film 11 is different from the distance between the other end of the range YL and the edge of the magnetic thin film 11, the shorter of the two distances is taken as Yd2. The distance Yd2 is preferably at least twice the diameter λ of the skyrmion 40. Thereby, the generation of the repulsive force in the Y-axis direction between the skyrmion 40 and the edge of the magnetic thin film 11 can be suppressed. For this reason, it becomes easier to move the skyrmion 40 in the y-axis direction.

[0062] The length H of the magnetic thin film 11 is preferably designed such that the distance Yd2 is at least twice the diameter λ of the skyrmion 40. In the circuit in which the electric device 100 is mounted, when the ranges of the frequency and amplitude of the applied signal are determined, it is preferable to design the length H according to the frequency and amplitude. Also, at least one of the frequency and amplitude of the applied signal may be limited according to the length H of the magnetic thin film 11 so as to ensure the distance Yd2.

[0063] FIG. 11 is a diagram showing an example of the current density of the applied current and the time waveform of the emergent electric field. FIG. 11 shows the current density and the emergent electric field in the example described in FIGS. 9 and 10. As described in FIGS. 9 and 10, in this example, an alternating applied current flows along the longitudinal direction of the magnetic thin film 11. Also, a periodic emergent electric field is generated as the skyrmion 40 moves. The waveform of the emergent electric field corresponds to the voltage waveform applied between the pair of first electrodes 12.

[0064] As shown in FIG. 11, it can be seen that the phase of the spontaneous electric field lags behind the phase of the current density by a phase difference Δ2. That is, the electric device 100 functions as an element having an inductance component with respect to the alternating applied signal. In this specification, an element having an inductance component is referred to as an inductor. The electric device 100 may function as an element combining an inductance component and a resistance component. As the phase lag of the spontaneous electric field approaches 90 degrees, the electric device 100 will operate as a pure inductor.

[0065] As shown in FIG. 11, by flowing an applied current corresponding to the applied signal in the longitudinal direction of the magnetic thin film 11, the electric device 100 can be made to function as an inductor. Since the magnetic thin film 11 only needs to have a size corresponding to the diameter λ of the skyrmion 40, a small capacitor can be easily realized.

[0066] When the distance Yd2 becomes smaller than twice the diameter λ of the skyrmion 40, as in the example of FIG. 8, distortion occurs in the waveform of the spontaneous electric field. For this reason, the distance Yd2 is preferably not less than twice the diameter λ of the skyrmion 40.

[0067] FIG. 12 is a table showing the phase difference between the spontaneous electric field and the current density when the length H of the magnetic thin film 11 and the current density j0 of the applied current are changed. In this example, an applied current is flowing in the short direction of the magnetic thin film 11. In this example, the width W of the magnetic thin film 11 is set to be 1 times the diameter λ of the skyrmion 40. Also, the frequency of the applied current is 5 MHz.

[0068] FIG. 12 shows the length H of the magnetic thin film 11 being changed from 1 times to 12 times the diameter λ of the skyrmion 40, and the current density j0 being changed from 0 to 2×10 10 (A / m 2It shows the phase difference when it is changed up to . Each numerical value within the region surrounded by the square in Fig. 12 indicates the phase difference. When the sign of the phase difference is negative, it indicates that the phase of the generated electric field is ahead of the phase of the current density. That is, it indicates that the electric device 100 has a capacitance component. When the sign of the said phase difference is positive, it indicates that the phase of the generated electric field lags behind the phase of the current density. That is, it indicates that the electric device 100 has an inductance component.

[0069] In the table of Fig. 12, the region of H / λ and the current density j0 where the electric device 100 operates as a capacitor is defined as the capacitor region. Also, the region where the electric device 100 operates as an inductor is defined as the inductor region. The region that is neither the capacitor region nor the inductor region is a distorted region where distortion occurs in the waveform of the generated electric field.

[0070] The larger the length H, the larger the distance Yd1 shown in Fig. 5. Therefore, in this example, in the region where H / λ is 10 or more, there exists a capacitor region where there is no distortion in the waveform of the generated electric field. However, as the current density j0 increases, the range YC increases and the distance Yd1 decreases. For this reason, the region where the current density j0 is 0.5×10 10 (A / cm 2 ) or more is a distorted region. Note that in the region where H / λ is 2 or less, there exists an inductor region where the electric device 100 operates as an inductor.

[0071] Fig. 13 is a table showing the phase difference between the generated electric field and the current density when the length H of the magnetic thin film 11 and the current density j0 of the applied current are changed. In this example, the frequency of the applied current is 50 MHz. Other conditions are the same as in the example of Fig. 12.

[0072] As the frequency of the applied current increases, it becomes difficult for the skyrmion 40 to move following the fluctuation of the applied current. For this reason, the range YC becomes smaller and the distance Yd1 becomes larger. For this reason, in the example of Fig. 13, compared with the example of Fig. 12, the capacitor region exists up to the region where H / λ is smaller and the current density j0 is larger.

[0073] FIG. 14 is a table showing the phase difference between the induced electric field and the current density when the length H of the magnetic thin film 11 and the current density j0 of the applied current are changed. In this example, the frequency of the applied current is 500 MHz. Other conditions are the same as those in the example of FIG. 12.

[0074] In FIG. 14, the frequency of the applied current is even higher. For this reason, in the example of FIG. 14, compared with the example of FIG. 13, the H / λ is smaller, and a capacitor region exists up to the region where the current density j0 is large.

[0075] FIG. 15 is a table showing the phase difference between the induced electric field and the current density when the length H of the magnetic thin film 11 and the current density j0 of the applied current are changed. In this example, the frequency of the applied current is 2.5 GHz. Other conditions are the same as those in the example of FIG. 12.

[0076] In FIG. 15, the frequency of the applied current is even higher. For this reason, in the example of FIG. 15, compared with the example of FIG. 14, the H / λ is smaller, and a capacitor region exists up to the region where the current density j0 is large. However, a strain region has occurred in some regions.

[0077] FIG. 16 is a table showing the phase difference between the induced electric field and the current density when the length H of the magnetic thin film 11 and the current density j0 of the applied current are changed. In this example, the frequency of the applied current is 5 GHz. Other conditions are the same as those in the example of FIG. 12. In this example, the entire region shown in FIG. 16 was a strain region.

[0078] As shown in FIGS. 12 to 16, whether the electric device 100 functions as a capacitor is determined by the length H, the current density j0 of the applied current, and the frequency. The electric device 100 preferably has a length H such that it can function as a capacitor.

[0079] In FIGS. 12 to 16, the capacitor region in which the electric device 100 can function as a capacitor when an applied current is passed in the short side direction of the magnetic thin film 11 was described. The inductor region when an applied current is passed in the longitudinal direction of the magnetic thin film 11 also shows a tendency similar to that of the capacitor region shown in FIGS. 12 to 16. The electric device 100 preferably has a length H such that it can function as an inductor.

[0080] As shown in FIGS. 12 to 16, even when an applied current is passed in the short side direction of the magnetic thin film 11, the electric device 100 may function as an inductor. Also, depending on the frequency of the applied current, whether the electric device 100 functions as a capacitor or an inductor may switch. For example, when H / λ = 2, as shown in FIGS. 12 and 13, an electric device 100 that functions as an inductor when the frequency of the applied current is low and functions as a capacitor when the frequency of the applied current is high can be realized.

[0081] FIG. 17 is a diagram showing another example of the electric device 100. The electric device 100 in this example further includes a pair of second electrodes 14, a switch 16, and a control unit 20 with respect to the configuration of the electric device 100 described in FIGS. 1 to 16. Other structures are the same as those of the electric device 100 in any of the aspects described in FIGS. 1 to 16. For example, the size of the magnetic thin film 11 is the same as that in any of the aspects described in FIGS. 1 to 16.

[0082] The pair of first electrodes 12 and the pair of second electrodes 14 are connected to the magnetic thin film 11. As described above, the pair of first electrodes 12 pass a current in the first direction on the main surface of the magnetic thin film 11. The pair of second electrodes 14 pass an applied current in a second direction different from the first direction on the main surface of the magnetic thin film 11. The length of the magnetic thin film 11 in the first direction is different from the length of the magnetic thin film 11 in the second direction. In this example, the length of the magnetic thin film 11 in the first direction is longer than the length of the magnetic thin film 11 in the second direction. In the example of FIG. 17, the first direction is the longitudinal direction of the magnetic thin film 11, and the second direction is the short side direction of the magnetic thin film 11.

[0083] The switch 16 switches which of the pair of first electrodes 12 and the pair of second electrodes 14 to pass the applied current through. That is, the switch 16 selects either the first electrode 12 or the second electrode 14, and causes the selected pair of electrodes to function as the two input / output terminals I / O of the electric device 100. The electric device 100 in this example has a set of switches 16-1 and 16-2. The switch 16-1 selects either the first electrode 12-1 or the second electrode 14-1 and functions as one of the input / output terminals I / O. The switch 16-2 selects either the first electrode 12-2 or the second electrode 14-2 and functions as the other input / output terminal I / O.

[0084] The control unit 20 controls which of the pair of first electrodes 12 and the pair of second electrodes 14 to pass the applied current through according to whether the electric device 100 operates as an inductor or a capacitor. The control unit 20 in this example passes the applied current in the first direction (longitudinal direction) when the electric device 100 operates as an inductor. The control unit 20 passes the applied current in the second direction (lateral direction) when the electric device 100 operates as a capacitor. Thereby, as described with reference to FIGS. 4 to 11, the electric device 100 can operate as an inductor or a capacitor.

[0085] The control unit 20 in this example controls which of the pair of first electrodes 12 and the pair of second electrodes 14 to pass the applied current through by controlling the switch 16. Whether the electric device 100 operates as an inductor or a capacitor may be fixedly set by the user or the like according to the use of the electric device 100, or may be dynamically determined by the control unit 20 according to a preset determination criterion. According to the electric device 100 in this example, both an inductor and a capacitor can be realized with one element.

[0086] Figure 18 is a diagram showing another example of the electrical device 100. The electrical device 100 in this example further includes at least one of the skyrmion generation unit 30 and the position adjustment unit 42 with respect to the configuration of the electrical device 100 described in FIGS. 1 to 17. Other structures are the same as those of the electrical device 100 in any of the aspects described in FIGS. 1 to 17. In FIG. 18, an example of an arrangement in which a pair of first electrodes 12 sandwich the magnetic thin film 11 in the longitudinal direction is shown, but the arrangement of the electrodes with respect to the magnetic thin film 11 may be the same as that in FIG. 4 or may be the same as that in FIG. 17.

[0087] The skyrmion generation unit 30 locally applies a magnetic field to the magnetic thin film 11 to generate skyrmions 40 in the magnetic thin film 11. The skyrmion generation unit 30 may have a coil 32 that generates a local magnetic field in a direction perpendicular to the main surface of the magnetic thin film 11. The skyrmion generation unit 30 may generate a local magnetic field by passing an electric current through the coil 32. Skyrmions 40 are generated in a region of the main surface of the magnetic thin film 11 where the local magnetic field from the coil 32 is applied. In each of the aspects described in FIGS. 1 to 17, the skyrmion generation unit 30 may be provided.

[0088] A magnetic field may be applied to the entire magnetic thin film 11 by a magnetic field application unit different from the coil 32. The magnetic field application unit is, for example, a permanent magnet. A magnetic field of about 0.6 T is applied to the entire magnetic thin film 11 by the magnetic field application unit. The coil 32 generates a local magnetic field such that the combined magnetic field with the magnetic field by the magnetic field application unit is about -50 mT. In a region where the local magnetic field by the coil 32 is not applied, a magnetic field of about 0.6 T is continuously applied by the magnetic field application unit. The coil 32 generates a local magnetic field for a time of about several ns. Thereby, skyrmions 40 are generated. After the skyrmions 40 are generated, a magnetic field of about 0.6 T is applied to the entire magnetic thin film 11. The size of the region where the coil 32 applies a local magnetic field in the x-axis direction may be the same as W. The size of the region in the y-axis direction may be about half of the diameter λ of the skyrmion 40.

[0089] When it is desired to erase the skyrmion 40, a DC erasing current of about 1×10 11 A / m 2 is passed through the magnetic thin film 11. The erasing current may flow in the short side direction. Due to a relatively large erasing current, the skyrmion 40 collides with the edge of the magnetic thin film 11 and disappears.

[0090] The position adjuster 42 adjusts the position of the skyrmion 40 in the longitudinal direction by passing a DC current in the longitudinal direction of the magnetic thin film 11. Since the skyrmion 40 moves according to the current flowing on the main surface of the magnetic thin film 11, the position of the skyrmion 40 can be adjusted by passing a DC current through the magnetic thin film 11. The position adjuster 42 adjusts the direction in which the skyrmion 40 moves by adjusting the positive and negative signs of the DC current. For example, by passing a DC current from the first electrode 12-1 to the first electrode 12-2, the skyrmion 40 can be moved in that direction. The position adjuster 42 adjusts the amount of movement of the skyrmion 40 by adjusting at least one of the magnitude of the DC current and the length of the time for which the DC current is applied. The larger the DC current, the larger the amount of movement of the skyrmion 40, and the longer the application time of the DC current, the larger the amount of movement of the skyrmion 40.

[0091] The position adjuster 42 may move the skyrmion 40 to the center in the longitudinal direction of the magnetic thin film 11. By passing an alternating applied current in this state, the distances Yd1 and Yd2 described in FIGS. 5 and 10 can be increased.

[0092] The control unit 20 in this example may control the skyrmion generation unit 30 and the position adjuster 42 to generate a plurality of skyrmions 40 on the main surface of the magnetic thin film 11. Each skyrmion 40 is arranged at a predetermined interval in the longitudinal direction of the magnetic thin film 11.

[0093] The greater the number of skyrmions 40 present in the magnetic thin film 11, the greater the emergent magnetic field when an alternating applied current is applied. Therefore, the gain of the emergent electric field with respect to the applied current can be increased. Accordingly, the inductance value and capacitance value of the electric device 100 can be controlled by the number of skyrmions 40. The control unit 20 may control the number of skyrmions 40 arranged in the longitudinal direction based on the inductance value or capacitance value that the electric device 100 should have. According to this example, an electric device 100 with a variable inductance value or capacitance value can be realized.

[0094] FIG. 19 shows an example in which a plurality of skyrmions 40 are present in the magnetic thin film 11. In FIG. 19, an example of an arrangement in which a pair of first electrodes 12 sandwich the magnetic thin film 11 in the longitudinal direction is shown, but the arrangement of the electrodes with respect to the magnetic thin film 11 may be the same as in FIG. 4 or the same as in FIG. 17. The control unit 20 may generate a plurality of skyrmions 40 arranged in the longitudinal direction of the magnetic thin film 11 by repeating the generation of skyrmions 40 by the skyrmion generation unit 30 and the movement of the skyrmions 40 by the position adjustment unit 42.

[0095] For example, after the skyrmion generation unit 30 generates the first skyrmion 40-1, the position adjustment unit 42 flows a direct current from the first electrode 12-1 toward the first electrode 12-2. As a result, the skyrmion 40-1 moves in a direction approaching the first electrode 12-2. After moving the skyrmion 40 by a predetermined distance, the skyrmion generation unit 30 generates a second skyrmion 40-2. The position adjustment unit 42 moves the two skyrmions 40 in a direction approaching the first electrode 12-2. After moving the two skyrmions 40 by a predetermined distance, the skyrmion generation unit 30 generates a third skyrmion 40-3.

[0096] The interval Yd3 between the skill ions 40 can be controlled by the magnitude and application time of the direct current after generating each skill ion 40. By repeating such a process, a plurality of skill ions 40 arranged at a predetermined interval can be generated. In response to the applied alternating current, each skill ion 40 vibrates while generally maintaining the interval Yd3.

[0097] The control unit 20 may control the skill ion generation unit 30 and the position adjustment unit 42 so that the interval Yd3 is equal to or greater than twice the diameter λ of the skill ion 40. By setting the distance between the skill ions 40 to be 2×λ or more, the influence of the repulsive force between the skill ions 40 can be reduced, and the skill ion 40 can be moved in the y-axis direction. Thereby, the distortion of the waveform of the emergent electric field can be reduced.

[0098] Each skill ion 40 has the ranges YC and YL described in FIGS. 5 and 10. For each skill ion 40, it is preferable that the distances Yd1 and Yd2 are equal to or greater than twice the diameter λ of the skill ion 40. That is, in both of the two skill ions 40 arranged at both ends in the longitudinal direction, it is preferable that the distances Yd1 and Yd2 are equal to or greater than twice the diameter λ of the skill ion 40. Thereby, the influence of the repulsive force from the end sides in the longitudinal direction of the magnetic thin film 11 can be reduced.

[0099] The distances Yd1 and Yd2 change according to the frequency and amplitude of the applied current. The control unit 20 may set an upper limit value for the number of skill ions 40 formed in the magnetic thin film 11 based on the frequency and amplitude of the applied current. The upper limit value may be set so that the distances Yd1 and Yd2 are equal to or greater than twice the diameter λ of the skill ion 40.

[0100] When the control unit 20 wants to reduce the number of skyrmions 40, a relatively large DC erasing current is passed through the magnetic thin film 11. The erasing current may be a current in the short side direction of the magnetic thin film 11 or a current in the long side direction. By passing a large erasing current, the skyrmions 40 collide with the edge of the magnetic thin film 11 and the skyrmions 40 are erased. The control unit 20 may cause a plurality of skyrmions 40 to collide with the edge of the magnetic thin film 11 and be erased all at once by passing an erasing current in the short side direction of the magnetic thin film 11. The control unit 20 may sequentially cause each skyrmion 40 to collide with the edge of the magnetic thin film 11 by passing an erasing current in the long side direction of the magnetic thin film 11, thereby sequentially reducing the number of skyrmions 40. In this case, the control unit 20 may adjust the number of skyrmions 40 to be erased by adjusting the time for which the erasing current is passed.

[0101] FIG. 20 is a diagram showing an example of a memory element 200 according to a second embodiment of the present invention. The memory element 200 in this example stores information depending on the presence or absence of skyrmions 40 in the magnetic thin film 11. The memory element 200 in this example includes a magnetic thin film 11, a pair of first electrodes 12, a skyrmion generation unit 30, a current application unit 50, and a detection unit 60. The memory element 200 may further include a magnetic field application unit such as a permanent magnet. The magnetic thin film 11 and the pair of first electrodes 12 are the same as the electric device 100 described with reference to FIGS. 1 to 19. FIG. 20 shows an example of an arrangement in which a pair of first electrodes 12 sandwich the magnetic thin film 11 in the longitudinal direction, but the arrangement of the electrodes with respect to the magnetic thin film 11 may be the same as that in FIG. 4 or the same as that in FIG. 17.

[0102] The skyrmion generation unit 30 generates skyrmions 40 by applying a local magnetic field to the magnetic thin film 11. The presence or absence of one skyrmion 40 corresponds to 1-bit information. The current application unit 50 may erase the skyrmions 40 by passing the above-described erasing current through the magnetic thin film 11.

[0103] The detection unit 60 detects the phase difference between the emergent electric field generated when an alternating current is passed through the magnetic thin film 11 and the alternating current, and detects the presence or absence of the skyrmion 40 based on the phase difference. The current application unit 50 may apply an alternating current to the first electrode 12. The detection unit 60 may include a voltmeter that measures the voltage between the pair of first electrodes 12. The detection unit 60 may obtain information indicating the phase of the alternating current from the current application unit 50, and may also include an ammeter that measures the alternating current applied to the first electrode 12.

[0104] When the skyrmion 40 is present in the magnetic thin film 11, a predetermined phase difference occurs between the emergent electric field and the alternating current. As described with reference to FIGS. 12 to 16, the phase difference is determined by the length H of the magnetic thin film 11, the frequency of the alternating current, and the current density. The detection unit 60 may determine whether the skyrmion 40 is present in the magnetic thin film 11 by comparing the detected phase difference with a reference value determined by the length H of the magnetic thin film 11, the frequency of the alternating current, and the current density. The reference value can be measured in advance as described with reference to FIGS. 12 to 16. The reference value is preset in the detection unit 60. The detection unit 60 may determine that the skyrmion 40 is present when the difference between the detected phase difference and the reference value is equal to or less than a predetermined value.

[0105] According to this example, the presence or absence of the skyrmion 40 can be detected without directly observing the emergent magnetic field of the skyrmion 40. Therefore, it is not necessary to provide a magnetic field detection device such as a tunneling magnetoresistance element (TMR element) for detecting the emergent magnetic field of the skyrmion 40. Therefore, the memory element 200 can be miniaturized.

[0106] As described above, the present invention has been described using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is obvious to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that forms with such changes or improvements can also be included in the technical scope of the present invention.

Description of Reference Numerals

[0107] 11 ··· Magnetic thin film, 12 ··· First electrode, 14 ··· Second electrode, 16 ··· Switch, 20 ··· Control unit, 30 ··· Skymion generation unit, 32 ··· Coil, 40 ··· Skymion, 42 ··· Position adjustment unit, 50 ··· Current application unit, 60 ··· Detection unit, 100 ··· Electric device, 200 ··· Memory element

Claims

1. An electrical device that operates as at least one of an inductor and a capacitor, a magnetic thin film in which at least a skyrmion crystal phase and a ferromagnetic phase in which skyrmions are generated in response to an applied magnetic field are exhibited, a pair of first electrodes connected to the magnetic thin film and flowing an alternating applied current corresponding to an alternating applied signal applied to the inductor or the capacitor in a first direction on a main surface of the magnetic thin film comprising An electrical device in which a pair of the first electrodes functions as two terminals of the inductor or the capacitor.

2. The first direction is the longitudinal direction of the main surface of the magnetic thin film, The electrical device operates as the inductor The electrical device according to claim 1.

3. The first direction is the short-side direction of the main surface of the magnetic thin film, The electrical device operates as the capacitor The electrical device according to claim 1.

4. a pair of second electrodes connected to the magnetic thin film and flowing the applied current in a second direction different from the first direction on the main surface of the magnetic thin film, a control unit that controls which of the pair of first electrodes and the pair of second electrodes the applied current flows through according to whether the electrical device operates as either the inductor or the capacitor The electrical device according to claim 1, comprising.

5. The length of the main surface of the magnetic thin film in the first direction is longer than the length of the main surface of the magnetic thin film in the second direction, When the control unit operates the electrical device as the inductor, the applied current is caused to flow in the first direction, and when the electrical device is operated as the capacitor, the applied current is caused to flow in the second direction The electrical device according to claim 4.

6. The length of the magnetic thin film in the first direction is 5 times or more the diameter of the skyrmion The electrical device according to claim 2 or 5.

7. The length of the magnetic thin film in the second direction is 1 time or more the diameter of the skyrmion The electrical device according to claim 5.

8. The length of the magnetic thin film in the second direction is 2 times or less the diameter of the skyrmion The electrical device according to claim 7.

9. further comprising a skyrmion generation unit that locally applies a magnetic field to the magnetic thin film to generate the skyrmion in the magnetic thin film The electrical device according to claim 1.

10. The first direction is the longitudinal direction of the main surface of the magnetic thin film, further comprising a position adjustment unit that adjusts the position of the skyrmion in the first direction by flowing a direct current in the first direction The electrical device according to claim 9.

11. further comprising a control unit that generates a plurality of skyrmions arranged in the first direction of the magnetic thin film by repeating the generation of the skyrmion by the skyrmion generation unit and the movement of the skyrmion by the position adjustment unit The electrical device according to claim 10.

12. The control unit controls the skyrmion generation unit and the position adjustment unit so that the distance between the skyrmions arranged in the first direction is equal to or more than twice the diameter of the skyrmion. The electrical device according to claim 11.

13. The control unit controls the number of skyrmions arranged in the first direction based on the inductance value or capacitance value that the electrical device should have. The electrical device according to claim 11 or 12.

14. A memory element that stores information according to the presence or absence of skyrmions, a magnetic thin film in which at least a skyrmion crystal phase and a ferromagnetic phase in which the skyrmion is generated appear in response to an applied magnetic field, a pair of first electrodes connected to the magnetic thin film and flowing a current in a first direction on the main surface of the magnetic thin film, a current application unit that applies an alternating current to the first electrode, a detection unit that detects the phase difference between the induced electric field generated when the alternating current flows and the alternating current, and detects the presence or absence of the skyrmion based on the phase difference A memory element comprising.

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