JP6507147B2 - Magnetic element and skyrmion memory - Google Patents

Description

  The present invention relates to a magnetic element capable of generating skirmion, a skirmion memory to which the magnetic element is applied, a CMOS-LSI device equipped with skirmion memory, a personal computer, a data recording medium, a data recording device, a mobile phone, a smart phone, a digital The present invention relates to a camera, a stick memory, a communication device, an image recording device, a television receiver, a self-propelled device, a flight device, and a space flight device.

  The demand for increased storage capacity does not know to stay. The number of pixels of the image element increases, the required storage amount is equivalent to 1 Mbit, and the moving picture has an information amount exceeding 1 Gbit.

  Corresponding to this, the storage capacity of the storage device is being further increased from 1 T bits. In addition, SD cards for imaging devices such as cameras and video cameras are also increasing in capacity.

  A magnetic element utilizing a magnetic structure of a magnetic substance as a storage bit has secured its status as a mass storage device. Magnetic elements can hold nanoscale magnetic structures without power consumption, and are becoming increasingly important as memory devices for electronic devices.

  Furthermore, in recent years, research and development of magnetic memory CMOS mixed devices for mounting a non-volatile memory on a CMOS device fabricated on a silicon substrate and aiming at a dramatic improvement in calculation processing capacity have been energetically conducted.

  The purpose of this is to omit the control circuit and shorten the control time accompanying the exchange of signals between the silicon chip composed of CMOS circuits and the non-volatile element chip, a technology to dramatically improve the calculation processing time It is.

  Furthermore, this research and development aims at development of the ultra power saving device which cut off the power to a useless circuit part. In particular, power saving of CMOS-LSI devices has emerged as an important issue in recent years, and the importance of solving the issue of reducing standby power is increasing.

  When these technologies are realized, large-scale memory can be used to handle large-scale information, and its response (write, read, erase) is fast, has a human interface with high functionality and excellent operability, and Low-power personal computers, data recording media, data recording devices, mobile phones, smart phones, digital cameras, stick memories, communication devices, image recording devices, televisions, self-propelled devices, flight devices, space flight devices, etc. Realization is expected.

  Under these circumstances, the present inventors have found a material having a skyrmion magnetic structure in a chiral magnetic material under an external magnetic field and also found that the skyrmion can be driven by an electric current, and this magnetic structure was used. A magnetic element has been proposed (Patent Document 1).

  Skirmions have a spiral magnetic structure with a magnetic moment antiparallel to the applied magnetic field at the center and a magnetic moment parallel to the applied magnetic field at the periphery.

  Skirmion is expected to be applied as a large-capacity storage magnetic element that has a nanoscale-sized magnetic structure with a diameter of 1 to 100 nm, and can make enormous bit information extremely fine and store it. The skyrmion is also a magnetic structure that can directly transfer this bit information and can be applied to information calculation and transmission.

  From these characteristics, the skyrmion element is assumed to be the basis of a next-generation magnetic memory device that gives breakthroughs to the performance limits of data recording media and magnetic memories for data recording devices, the storage capacity of which is continuously increasing. It is expected.

  In particular, magnetic memory is highly resistant to various elementary particles and radiation in space. The skyrmion memory also has the same features. Also, such a large capacity magnetic memory does not require a rotating mechanism such as a motor. Therefore, large capacity magnetic memory is expected to occupy a leading role of memory in space.

  On the other hand, a flash memory that uses electrons recently emerging as a memory medium as storage bits is not suitable for such an environment. Electrons easily go over the energy barrier of the silicon oxide film by high energy elementary particles and radiation, causing data erasure and erroneous writing.

  In addition, integration of large-scale nonvolatile Skirmion memory with large-scale logic CMOS-LSI devices on the same chip is very attractive for low power consumption CMOS devices and high-intelligent CMOS devices. It is expected that the high density non-volatile Skirmion memory embedded CMOS-LSI device to which the

  As another candidate for such a next-generation memory magnetic device, a magnetic shift register 1 has been proposed which drives magnetic domain walls centered on IBM in the United States, transfers its magnetic moment arrangement by current, and reads stored information. (See Patent Document 2).

  FIG. 16 is a schematic view showing the principle of magnetic domain domain wall driving by current. Boundaries of magnetic regions in which the directions of magnetic moments are opposite to each other are domain domain walls. The current in the direction of the arrow drives the magnetic domain domain wall. A magnetic change due to the direction of the magnetic moment storing the information constituting the domain, which is caused by the movement of the domain domain wall, is detected by the lower magnetic sensor 2 to extract the magnetic information.

  However, such a magnetic shift register 1 has a disadvantage that a large current is required to move the magnetic domain domain wall, and the transfer speed of the magnetic domain domain wall is slow. As a result, there are problems such as delay in writing to memory and increase in time required for erasing.

  Therefore, the inventor of the present invention has proposed a skyrmion magnetic element using skyrmions generated in a magnetic body as a storage unit (see Patent Document 1). In this proposal, the inventors have shown that the skillion can be driven by current.

  In the past, the magnetic bubble was moved onto the edge by fixing the magnetic bubble to the edge of a material such as permalloy having a specific shape and rotating the magnetic field. That is, in a magnetic element memory using magnetic bubbles, a rotating magnetic field has always been required.

  On the other hand, the present inventors have shown that it is possible to drive this directly with an electric current instead of a rotating magnetic field while using skirmions instead of magnetic bubbles.

As described above, since skyrmion can be generated, erased and moved by current, it is expected to be applied as a magnetic element capable of controlling generation, erasure and movement of magnetic information.
[Prior art document]
[Patent Document]
Patent Document 1 Japanese Patent Application No. 2012-232324
Patent Document 2 US Pat. No. 6,834,005
[Non-patent literature]
Non-Patent Document 1 Naoto Naganaga, Yoshinori Tokura, "Topological properties and dynamics of magnetic skyrmions", Nature Nanotechnology, UK, Nature Publishing Group, Dec. 4, 2013, Vol. 8, p 899-911.

  As mentioned above, there is a growing expectation that Skillmions will be applied to devices such as memories and logical operations, but the detailed relationship between the generation of Skillmions and the magnetic field etc. has not been clarified. It was a situation that could not be realized.

  Therefore, the inventor of the present application clarified the detailed relationship between the generation of skyrmions and the applied magnetic field and the like, and developed a magnetic element and a skyrmion memory capable of generating skyrmions.

  That is, the present invention relates to a magnetic element capable of generating skirmion with low power consumption, a skirmion memory to which the magnetic element is applied, a CMOS-LSI device incorporating skirmion memory, and a personal computer incorporating the skirmion memory, data A recording medium, data recording device, mobile phone, smart phone, digital camera, stick memory, communication device, image recording device, television receiver, self-propelled device, flight device and space flight device.

A magnetic element according to a first aspect of the present invention is a thin layer magnetic element capable of generating skyrmions, and a thin layer lower magnetic body that becomes a skyrmion phase and a ferromagnetic phase according to the applied magnetic field strength ; A predetermined area including the end of the lower magnetic body is provided on one surface side of the lower magnetic body so as to surround the predetermined area, and a current flows, thereby causing the second magnetic field to travel in the direction opposite to the first magnetic field applied to the lower magnetic body. And a current circuit generated in a predetermined region .

  A magnetic element according to a second aspect of the present invention is the magnetic element according to the first aspect, wherein the current circuit has a width W, which is a length in the extending direction of the end of the predetermined area, relative to a diameter λ of the skyrmion. It is characterized in that it is provided to surround the predetermined area in the range of λ ≧ W> λ / 4.

  A magnetic element according to a third aspect of the present invention is the magnetic element according to the first or second aspect, wherein the current circuit has a height h which is a length in a direction perpendicular to the extending direction of the end portion of the predetermined area. It is characterized in that it is provided to surround the predetermined area in the range of 2λ> h> λ / 2 with respect to the diameter λ of the skyrmion.

  A magnetic element according to a fourth aspect of the present invention is the magnetic element according to any one of the first to third aspects, wherein the lower magnetic body has a notch formed at the end in the predetermined area, A length L of a tangent of the notch and the predetermined area is in a range of λ> L> λ / 2.

The magnetic element according to the fifth invention is the magnetic element according to any one of the first to fourth inventions, wherein the lower magnetic body has a width of Wm and a height of hm, and the diameter of the generated skyrmion For λ
2λ>Wm> λ / 2
2λ>hm> λ / 2
If the width of the predetermined area is W and the height is h,
λ ≧ W> λ / 4
2λ>h> λ / 2
It is provided so that the said predetermined area which becomes these may be enclosed.

A magnetic element according to a sixth aspect of the present invention is the magnetic element according to any one of the first to fourth aspects, wherein the current circuit is biased more than the center of one end of the lower magnetic body on one side of the lower magnetic body. Assuming that the lower magnetic body has a width of Wm and a height of hm, the lower magnetic body is provided with respect to the diameter λ of the generated skyrmion.
2λ>Wm> λ
2λ>hm> λ
The current circuit has a width W of the predetermined area, a height h, and the current circuit and one end of the lower magnetic body and the other end closest to the other end adjacent to the other end. Assuming that the width of the gap is d,
W = 0.4 × λ
h = λ / 2
0.4 × λ>d> 0.2λ
It is provided so that the said predetermined area which becomes these may be enclosed.

A magnetic element according to a seventh invention is the magnetic element according to any one of the first to third inventions, wherein the current circuit includes an end of the lower magnetic body on one side of the lower magnetic body. The region and the second region adjacent to the first region are provided on the side opposite to the end portion, and the lower magnetic body has a width of Wm and a height of hm, and the diameter of the skyrmion to be generated For λ
2λ>Wm> λ / 2
2λ>hm> λ / 2
And the first region surrounded by the current circuit has a width of 0.4 × λ parallel to the end and a height 0.6 × perpendicular to the end. The second region surrounded by the current circuit has a width of 0.4 × λ parallel to the end and a height 0.4 × λ perpendicular to the end. It is characterized by

  A magnetic element according to an eighth invention is characterized in that, in the magnetic element according to any one of the first to seventh inventions, the lower magnetic body is made of a chiral magnetic body.

  A magnetic element according to a ninth aspect is the magnetic element according to any one of the first to seventh aspects, wherein the lower magnetic body is made of a dipole magnetic body.

  A magnetic element according to a tenth aspect is the magnetic element according to any one of the first to seventh aspects, wherein the lower magnetic body is made of a frustrated magnetic body.

  The skyrmion memory according to an eleventh aspect of the present invention is a thin layer magnetic element capable of generating skyrmions, and is provided opposite to one surface side of the magnetic element, and can apply a first magnetic field to the magnetic element from a first direction. A magnetic field generation unit and a power supply capable of applying a current to the current circuit are provided, and the magnetic element is a magnetic element according to any one of the first to tenth inventions.

  The skyrmion memory according to the twelfth invention is the skyrmion memory according to the eleventh invention, wherein the power supply is weaker than the first magnetic field with respect to the current circuit of the magnetic element in a direction opposite to the first magnetic field. It is characterized in that a current can be applied to generate a second magnetic field to be directed.

  A skyrmion memory according to a thirteenth aspect of the present invention is a magnetic element according to the fifth aspect of the present invention, and a magnetic field generation unit provided opposite to one surface side of the magnetic element and capable of applying a first magnetic field to the magnetic element from a first direction. And a power supply capable of generating a second magnetic field in the current circuit by applying a current to the current circuit of the magnetic element.

  In a skillion memory according to a fourteenth aspect of the present invention, in the skillion memory according to the thirteenth aspect, the power supply generates, with respect to the current circuit, a generation pulse for generating the skillion and an erasing pulse for erasing the skillion. It is characterized in that it is possible to

  The skyrmion memory according to the fifteenth invention is characterized in that, in the skyrmion memory according to the fourteenth invention, the generated pulse is smaller than 0.015 J and the erase pulse is 0.04 J or more.

  A skyrmion memory according to a sixteenth aspect of the present invention is a magnetic element according to the sixth aspect, and a magnetic field generating portion provided opposite to one surface side of the magnetic element and capable of applying a first magnetic field to the magnetic element from a first direction. And a power supply capable of generating a second magnetic field in the current circuit by applying a current to the current circuit of the magnetic element.

  A skillion memory according to a seventeenth invention is the skillion memory according to the sixteenth invention, wherein the power supply generates, with respect to the current circuit, a generation pulse for generating the skillion and an erase pulse for erasing the skillion. It is characterized in that it is possible to

  According to an eighteenth aspect of the present invention, there is provided a skyrmion memory according to the seventeenth aspect, wherein the generated pulse is smaller than 0.015 J and the erase pulse is smaller than 0.02 J.

  A skyrmion memory according to a nineteenth aspect of the present invention is a magnetic element according to the seventh aspect of the present invention, and a magnetic field generation unit provided opposite to one surface side of the magnetic element and capable of applying a first magnetic field to the magnetic element from a first direction. And a power supply capable of generating a second magnetic field in the current circuit by applying a current to the current circuit of the magnetic element.

  A skillion memory according to a twentieth invention is the skillion memory according to the nineteenth invention, wherein the power supply generates, with respect to the current circuit, a generation pulse for generating the skillion and an erase pulse for erasing the skillion. It is characterized in that it is possible to

  According to a twenty-first aspect of the invention, there is provided a skyrmion memory according to the twentieth invention, wherein the generated pulse and the erase pulse have the same magnetic strength.

  A skillion memory according to a twenty-second invention is characterized in that, in the skillion memory according to the twenty-first invention, the generated pulse and the erase pulse are smaller than 0.015 J.

  A skyrmion memory according to a twenty-third aspect of the present invention is characterized in that, in the skyrmion memory according to the twentieth aspect, the erase pulse has a magnetic field intensity greater than that of the generated pulse.

  The skyrmion memory according to the twenty-fourth invention is characterized in that, in the skyrmion memory according to the twenty-third invention, the generated pulse is smaller than 0.015 J and the erase pulse is smaller than 0.02 J.

  According to a twenty-fifth aspect of the present invention, there is provided a CMOS-LSI device mounted with a skyrmion memory, wherein the skyrmion memory and the CMOS-LSI device according to any one of the eleventh to twenty-fourth aspects of the invention are formed in the same chip.

  A personal computer according to the twenty-sixth aspect is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth aspects is mounted.

  A data recording medium according to a twenty-seventh aspect of the invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth aspects of the invention is mounted.

  A data storage apparatus according to the twenty-eighth invention is characterized in that the skyrmion memory according to any one of the eleventh to twenty-fourth inventions is mounted.

  A mobile phone according to the twenty-ninth invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth inventions is mounted.

  A smartphone according to a thirtieth invention is characterized in that the skill-ion memory according to any one of the eleventh through twenty-fourth inventions is mounted.

  A digital camera according to a thirty-first aspect of the present invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth aspects of the present invention is mounted.

  A stick memory according to a thirty-second aspect of the present invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth aspects of the present invention is mounted.

  A communication apparatus according to a thirty-third aspect is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth aspects is mounted.

  An image recording apparatus according to a thirty-fourth aspect of the invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth aspects of the invention is mounted.

  A television receiver according to a thirty-fifth aspect of the present invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth aspects of the present invention is mounted.

  A self-propelled device according to a thirty-sixth invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth inventions is mounted.

  A flight apparatus according to the thirty-seventh invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth inventions is mounted.

  The space flight device according to the thirty-eighth invention is characterized in that the skyrmion memory according to any one of the eleventh through twenty-fourth inventions is mounted.

  According to the present invention having the above-described configuration, a magnetic element capable of generating skirmion with low power consumption, skirmion memory to which the magnetic element is applied, CMOS-LSI device incorporating skirmion memory, and skirmion memory Personal computer, data recording medium, data recording device, mobile phone, smart phone, digital camera, stick memory, communication device, image recording device, television, self-propelled device, flight device, space flight device be able to.

It is a schematic diagram which shows an example of the skyrmion which is a nano scale magnetic structure of the magnetic moment in a magnetic body. FIGS. 2A to 2E are schematic diagrams showing skillions having different phases. FIG. 2 is a schematic view showing a magnetic element that enables generation of skyrmions. It is a schematic diagram which shows the relationship between generation | occurrence | production of skyrmion and a magnetic field. FIG. 4A is a magnetic phase diagram of the chiral magnetic material, and FIG. 4B is a schematic view showing the time dependency of the magnetic field of the region A. As shown in FIG. It is a schematic diagram which shows skirmion production | generation in case an area | region becomes square shape. It is a schematic diagram which shows skirmion production | generation in case an area | region includes a magnetic material edge part. 6A is a schematic view in the case where the area A has the same height as the height of the magnetic body, and FIG. 6B is a schematic view in the case where the area is 1/2 the height of the magnetic body. FIGS. 7A to 7D are schematic diagrams showing skyrmion generation when the width of the region A is changed. FIGS. 8A to 8C are schematic diagrams showing skilmion generation according to the width of the region A and the presence or absence of the notch. FIGS. 9A and 9B are schematic diagrams showing skilmion generation when the height of the region A is changed. FIG. 18 is a schematic view showing a relationship between a magnetic field change of the region A and time when performing generation and deletion of skyrmions in Example 2. It is a schematic diagram which shows the time change of skyrmion production | generation and annihilation by the magnetic field change of the area | region A shown in FIG. 11 (A) shows the generation start state, FIG. 11 (B) shows the state where the skyrmion is generated, FIG. 11 (C) shows the state where the skyrmion is moved, and FIG. 11 (D) shows the sky state Indicates an erased state. FIG. 18 is a schematic view showing the generation and elimination of skyrmions in Example 3. FIG. 12A is a schematic view showing the relationship between the magnetic field Ha of the region A and time when the generation and elimination of skyrmions are performed, and FIG. 12B is a schematic view showing the magnetic element in the third embodiment. FIG. 18 is a schematic view showing the generation and elimination of skillion in Example 4. FIG. 13A is a schematic view showing the relationship between the magnetic field Ha of the region A and time when generation and deletion of skyrmions are performed, and FIG. 13B is a schematic view showing a magnetic element in the fourth embodiment. FIG. 13C is a schematic view showing the divided area A. FIGS. 14A to 14H are schematic diagrams showing other examples of the shape of the current circuit. It is a schematic diagram which shows the example of another shape of a current circuit. It is a schematic diagram which shows the principle of the magnetic domain drive by an electric current.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing an example of skirmion which is a nanoscale magnetic structure of magnetic moment in a magnetic substance. In FIG. 1, arrows indicate the direction of the magnetic moment.

  Skillmions consist of magnetic moments that point in all directions. When the direction of the magnetic field applied in the magnetic body is upward in the figure, the outermost magnetic moment is upward as well as parallel to the magnetic field as the direction of the magnetic field.

  The skyrmion is in the form of a plane rotating inward in a spiral from its outermost periphery, and along with this, the direction of the magnetic moment gradually changes its direction.

  And the magnetic moment which constitutes the center of the skyrmion will be stabilized downward so as to be antiparallel to the magnetic field.

  In Skirmion, the magnetic moment is regularly aligned while continuously changing its direction from downward to upward from the center to the outermost periphery, resulting in a structure in which a plurality of magnetic moments are regularly arranged like a vortex. There is. The directions of the magnetic moment at the center and the magnetic moment at the outermost periphery are antiparallel, and the direction from the center to the periphery is continuously twisted to form a spiral structure.

  Here, the nanoscale magnetic structure swirling in the magnetic material is characterized by the skyrmion number. The skyrmion number is expressed by the following [Equation 1] and [Equation 2] which indicates how many times the magnetic moment swirls per unit space. In Equation 2, the polar angle Θ (r) with the magnetic moment is a continuous function of the distance r from the center of the skyrmion, and when r is changed from 0 to 、, from π to zero or from zero to π Change.

An example of such a case of the number of skyrmions N _sk = ± 1 is shown in FIG. FIG. 2 is a schematic view showing skillions having different phases. FIG. 2E shows how to use the coordinates (right hand system). For the x-axis and y-axis, the z-axis is from the back of the paper to the front. Arrows indicate magnetic moments. The magnetic structure shown in FIG. 2 is in a state defined as skirmion.

  γ indicates the phase between magnetic moments. In FIG. 2, four examples (A) to (D) of different phases γ are shown.

  The directions of all the magnetic moments of (A) γ = 0 and (B) γ = π have the directions of the magnetic moments rotated by exactly 180 °.

  (C) [gamma] =-[pi] / 2 takes the direction of -90 degrees (90 degrees clockwise) for all the magnetic moment directions at [gamma] = 0. The skirmion of the phase λ = π / 2 in FIG. 2D corresponds to the skirmion of FIG.

  That is, although the magnetic structures of the four examples illustrated in FIGS. 2A to 2D appear to be different, they are topologically identical magnetic structures.

  The skyrmion having such a structure is stably present once generated, and acts as a carrier responsible for signal transmission in the chiral magnetic material under application of an external magnetic field.

Next, the motion of the skyrmion which is a nanoscale magnetic structure such a skyrmion number N _sk = ± 1 will be described below.

  FIG. 3 is a schematic view showing the magnetic element 10 which enables the generation and cancellation of skirmions. The magnetic element 10 is an element formed in a thin layer having a thickness of 500 nm or less, and is formed using a technique such as MBE (Molecular Beam Epitaxy) or sputtering.

  The magnetic element 10 includes a lower magnetic body 111 serving as a base and a current circuit 112 formed to face the upper surface of the lower magnetic body 111. The current circuit 112 in this example has a side perpendicular to the end of the lower magnetic body 111, a side parallel to the end of the lower magnetic body 111, and a side perpendicular to the end of the lower magnetic body again.

  The lower magnetic body 111 is a chiral magnetic body, and is formed of FeGe, MnSi, or the like.

  The current circuit 112 may be electrically isolated from the lower magnetic body 111 using an insulating material or the like. The current circuit 112 is formed of a metal material such as Cu, W, Ti, Al, Ni, Pt, Au, TiN, or AlSi.

  Hereinafter, the region surrounded by this current circuit is referred to as region A, and the magnetic field strength in region A is taken as Ha.

  A skyrmion memory is formed by including the magnetic element 10 and the magnetic field generator 12 as described above. The skill mion memory is a memory that uses the skill mion as bit information.

  The magnetic field generation unit 12 generates a magnetic field H, and is applied to the lower magnetic body 111 from the lower side of the paper surface of FIG. 3 (that is, from the back surface to the front surface of the lower magnetic body 111). Although only one magnetic field generation unit 12 is used in the present embodiment, the present invention is not limited thereto, and any magnetic field can be generated as long as the magnetic field can be applied perpendicularly to the lower magnetic body 111. The number and arrangement of the parts 12 are not limited, and a plurality of magnetic field generation parts 12 can also be used.

  Next, current is applied to the current circuit 112 in the direction indicated by the arrow C in FIG. 3 from an electrode (not shown). This current generates a magnetic field in the region A from the top downward (that is, from the front surface to the back surface of the lower magnetic body 111). Since the direction of the magnetic field induced by this current is opposite to the direction of the uniform magnetic field H, the direction from below to above the rectangular area A surrounded by the ends of the current circuit 112 and the lower magnetic body 111 The magnetic field Ha is weakened.

  As a result, it is possible to generate skill mions in a rectangular area.

  Next, the generation of skyrmions in chiral magnetics is demonstrated in detail in the Examples.

Example 1
In Example 1, the simulation experiment result of skyrmion production is shown.

  The movement of the skyrmion is described by the Landau-Lifshitz-Gilbert (LLG) equation. The following numerically solves the LLG equation with adiabatic, nonadiabatic spin transfer torque terms.

[Equation 3]
dM _r / dt = −γM _r × B _r ^eff + α / M · M _r × dM _r / dt

[Equation 4]
H =-J M M _r · (M _{r + ex} + M _{r + ey} )
−DΣ (M _r × M _{r + ex} · e _x + M _r × M _{r + ey} · e _y ) −− (B + Ha) · M _r

Here, [Equation 3] and [Equation 4] are associated by Br ^eff = −1 (1 / (hγ)) (∂H / ∂M _r ). γ = gμB / h (> 0) is the gyromagnetic ratio. h is Planck's constant. M _r represents a magnetic moment in a dimensionless amount. In the above [Equation 3] and [Equation 4], x indicates an outer product.

  Here, the Hamiltonian H represented by [Equation 4] is for the case of a chiral magnetic material. In the case of a dipole magnetic body or a frustrated magnetic body, the expression of H may be replaced with a description of each magnetic body.

  The dipole magnetic body is a magnetic body in which magnetic dipole interaction is important. In addition, the frustrated magnetic body is a magnetic body including a magnetic interaction space structure that favors a magnetic mismatch state.

  Next, the experimental conditions of the simulation experiment in this embodiment are shown in FIG.

  FIG. 4A is a schematic view showing the magnetic field dependency of the chiral magnetic body magnetic phase.

  The chiral magnetic substance is a magnetic substance which changes from the chiral magnetic phase to the skyrmion phase by the magnetic field strength Hsk and further changes from the skyrmion phase to the ferromagnetic phase at the strong magnetic field strength Hf. The chiral magnetic material used in this example has D = 0.18 J, M = 1, and α = 0.04. D is the magnitude of the Jaroshinski-Moriya interaction.

  Here, assuming that the magnitude of the magnetic exchange interaction of this magnetic substance is J, various physical quantities are described by values standardized by this amount.

  At low fields, the chiral magnet becomes a chiral phase with a magnetic structure of helical magnetic moments. When the magnetic field strength is increased, the chiral magnetic material is in the skirmion phase with the magnetic field strength Hsk = 0.0075J. Assuming that the skyrmion diameter at this time is λ, λ can be expressed as in the following [Equation 5] using J and D.

[Equation 5]
λ = 2√2 · πJ × a / D

  Here, a is a lattice constant. In chiral magnetic materials, the size of λ is several nanometers to hundreds of nanometers in size. Furthermore, in the chiral magnetic material used in the present embodiment, the ferromagnetic phase is obtained with Hf = 0.0252 J, which is a strong magnetic field strength.

  The time change of the magnetic field Ha of the area A in the simulation experiment is shown in FIG. 4 (B).

  First, the simulation experiment was started from the state in which the region A is in the ferromagnetic phase, with the magnetic field Ha of the region A of the chiral magnetic material being a magnetic field strength greater than Hf. Specifically, the magnetic field is applied in the direction from the bottom to the top (that is, the direction from the back surface to the surface of the lower magnetic body 111) with a magnitude of the magnetic field strength H = 0.03J. In this case, the ground state of the chiral magnet is a ferromagnetic phase in which skirmions do not exist.

  Next, the current starts flowing in the current circuit 112. At this time, the magnetic field Ha of the region A changes due to the magnetic field generated by the current of the current circuit 112.

  The current is applied such that the magnetic field Ha in the region A has a magnitude of 0.01 J at t = 1000 (hereinafter, unit 1 / J of t). Thereafter, a constant magnetic field strength of Ha = 0.01 J is maintained until t = 2000. When the application of current is stopped at t = 3000, the magnetic field intensity returns to the initial state, and Ha = 0.03J.

  Under this condition, simulation experiments are performed using the LLG equation. The simulation results regarding generation of skyrmions are shown in FIG. 5 to FIG.

  FIG. 5 is a schematic view showing skirmion generation in the case where the area A has a rectangular shape.

  The shape of region A is formed corresponding to the shape of current circuit 112. In the case of FIG. 5, the current circuit 112 is formed in a square shape, so that the shape of the region A formed corresponding to the shape of the current circuit 112 is also a square shape.

  The magnetic field Ha of this area | region A shows skirmion production | generation when it reduces from 0.03J to 0.01J by pulse current. It can be seen that skirmion S is not generated when the portion enclosed by the square does not contact the end of the magnetic material. Even if the magnetic field Ha of the region A is decreased to below the skimion phase Ha = Hsk or less, the skirmion S is not generated and the ferromagnetic phase is maintained.

  However, as seen in FIG. 6A, when the region A becomes a region including the end portion of the magnetic material, skirmions S are generated. As described above, the lower magnetic body 11 is made into the ferromagnetic phase by the magnetic field generation unit 12. For this reason, the magnetic moment in the lower magnetic body 11 points in the same direction as the magnetic field H applied by the magnetic field generator 12. However, the magnetic moment at the end of the lower magnetic body 11 does not turn in the same direction as the magnetic field H, and has a tilt with respect to the magnetic field H. For this reason, the end portion of the lower magnetic body 11 is more susceptible to skirmion S than other regions. By providing the current circuit 112 so as to surround the area including the end of the lower magnetic body 11, the skirmion S can be easily generated.

  From this, it can be seen that the inclusion of the magnetic material end is an essential condition for the generation of skyrmions. It is indicated that an energetically large wall exists between the ferromagnetic state having a uniform magnetic moment and the topological state of the skyrmion S.

  However, once the skyrmions S are formed into a uniform magnetic moment state, the skyrmions S are stably present. This is an important feature that guarantees the stability of Skillmion S as a carrier of information.

  Further, it can be understood from FIG. 6A that, if the width W which is the length in the spreading direction of the end portion of the region A is large, two skirmions S are generated on the left and right. When using as a magnetic element used for a memory, it is desirable that only one skyrmion S be generated in a predetermined area.

  Therefore, as shown in FIG. 6B, when the height h, which is the length in the direction perpendicular to the spreading direction of the end of the region A, is halved, two skyrmions S at the left end and one at the center The results to be generated were obtained.

  FIG. 7 shows the dependency of the skillion generation on the width W by fixing the height h of the region A to half and changing the width W for the skillion generation. The width W is gradually narrowed from FIG. 7 (A) to FIG. 7 (D).

  As a result of simulation, although two skyrmions S exist in FIGS. 7A and 7B, only one is present in FIGS. 7C and 7D. The width W in FIG. 7C is the same size as the diameter λ of the skyrmion S, and the width W in FIG. 7D is the same size as half the diameter λ of the skyrmion S.

  FIGS. 8A and 8B show the case where the width W of the region A is smaller than λ / 2. In this case, skill mions S are not generated.

  FIG. 8C shows that the skillion S can be generated when the cutout B at the end of the magnetic material is provided even if the width W is λ / 2. When the length of the tangent of the notch B to the region A when the notch B cuts the region A is L, it has been found that the skyrmion S can be generated in the range of λ> L> λ / 2. That is, the notches B of the magnetic body work effectively for skirmion generation.

  FIG. 9 shows the experimental results when the height h of the region A is lowered. As shown in FIG. 9A, one skyrmion S is generated in the range of 2λ> h> λ / 2. On the other hand, when h <λ / 2 in FIG. 9B, the skyrmion S can not be generated.

  The following things became clear from these simulation experiments.

(1) The right and left widths W of the region A are optimum in the following range.
λ ≧ W> λ / 4

(2) The height h of the region A is optimally in the following range.
2λ>h> λ / 2

(3) When installing a nonmagnetic notch B in the region A, a single skyrmion S can be generated if the tangent length L in the region A and the notch B is in the following range .
λ>L> λ / 2

(4) The magnetic field Ha of the region A necessary to generate a single skyrmion S is Ha <0.015 J. The upper limit value of this Ha is twice the magnetic field strength H _{sk at which} the lower magnetic body 11 is in the skirmion phase.

  (5) If the application time width (pulse width) T of the local magnetic field is 1000 (1 / J) or more, skirmions S are formed. Even for a longer time, the state generated by a single skillion S is maintained, and a plurality of skillions S will not be generated.

  The above simulation experiment results are very important in designing a magnetic element provided with skyrmion generation, giving a detailed design guideline of skyrmion generation by a magnetic field by applying a current.

  Thus, the present invention provides optimal design guidelines for the skyrmion generation method. Since the design rules can be described in standardized quantities in the skyrmion size, it is possible to give common design guidelines even for various magnetic materials. As a result, it can be expected that a large impact will be brought about in practicalizing a magnetic element using skirmion.

Example 2
In Example 2, the simulation experiment result of skyrmion elimination is shown.

  The motions of the skillmions at the time of eliminating the skillmions can be described using the LLG equation as in the case of the skillmion generation.

  The magnetic substance of the present example is the same chiral magnetic substance as that of Example 1. The magnetic phase diagram of the chiral magnetic material is given in FIG. 4 (A). The width of the magnetic body 111 is the same as the diameter λ of the skyrmion, and the height is also the same square shape as the length λ.

  The current circuit 112 is arranged so that an additional magnetic field can be applied to the region A shown in FIG. 11A, and is similar to the current circuit 112 shown in FIG.

  The region A is set to a region including the end of the magnetic body 111. The width of the region A was λ / 2, and the height h was 0.6 × λ.

  The magnetic field of region A is set to Ha. The magnetic field Ha of the area A in the case of eliminating the skyrmion S is shown in FIG.

  The chiral magnetic material is a ferromagnetic phase at time t = 0 and the magnetic field Ha = 0.03J.

  The skyrmion S is generated at a pulse magnetic field up to time t = 3000 (1 / J). At this time, one skirmion S is generated as shown in FIG. 11 (B) from the state of FIG. 11 (A). The generation conditions are the same as the conditions described in the first embodiment.

  Next, the magnetic field Ha of the region A is strengthened to erase the skyrmion S. Between time t = 5000 (1 / J) to 8000 (1 / J), a pulse magnetic field as shown in FIG. 10 with Ha = 0.05 J is applied to region A at maximum.

  During this time, as shown in FIG. 11C, the skyrmion S moves to the left end of the area A, and further moves to the lower part and disappears. Thereafter, with Ha = 0.03 J, the initial state shown in FIG. 11D is restored, and the erasure of the skirmion S is completed. The additional magnetic field strength at this time is +0.02 J, which is an amount obtained by inverting -0.02 J at the time of generation.

  As described above, the skyrmion S generated once can be eliminated by the increase of the magnetic field Ha of the region A. The conditions necessary for erasing at this time are as follows.

(6) The width Wm of the magnetic body is in the following range with respect to the skyrmion diameter λ.
2λ>Wm> λ / 2
If Wm is too small, skill mions are not generated. Wm is preferably about λ.

(7) The height hm of the magnetic body is in the following range with respect to the skyrmion diameter λ.
2λ>hm> λ / 2
If hm is too large, the skyrmion escapes from the current circuit and can not be erased when the skyrmion is erased.

  (8) The width W of the region A conforms to (1). That is, λ ≧ W> λ / 4.

  (9) The condition of the height h of the region A follows (2). That is, 2λ> h> λ / 2. Here, the height is set to 0.6 × λ.

  (10) The magnetic field Ha of the region A necessary for erasing is Ha ≧ 0.04 J.

[Example 3]
The third embodiment shows an example in which the skyrmions can be erased even if the direction of the applied pulse magnetic field for skyrmion cancellation is the same as the direction of the skyrmion generation pulses. In the third embodiment, the region A is set to a region including the end of the magnetic body 111. The current circuit 112 is formed at a position biased to the left from the center of the lower side of the magnetic body 111. In the present invention, the current circuit 112 may be formed at a position deviated to the left or right from the center of the lower side of the lower magnetic body 111, or may be a position deviated to the right.

  As shown in FIG. 12A, a generated pulse 1 as a magnetic field is applied to the magnetic element 10, and then an erasing pulse 2 as a magnetic field is applied.

  The erase pulse 2 at this time is magnetic field application in the same direction as the generated pulse 1. In this example, the magnetic field intensity of the erasing pulse 2 of the magnetic field Ha of the region A is set to a value 0.015 J which is smaller than 0.03 J corresponding to the ferromagnetic phase. The magnetic field strength of the generated pulse 1 is 0.01 J. At this time, as shown in FIG. 12B, if the area A is disposed on the left side, the generated skyrmion can be erased. However, if the region A is too close to the left end, the skyrmion can not be generated by the first magnetic field application.

  In this case, the width Wm and the height hm of the magnetic body need to be larger than λ. In this embodiment, it is set to 1.2 × λ. The reason for employing a magnetic body slightly larger than λ is to secure a space for the generated skyrmion to move to the center of the magnetic body.

  The conditions required to eliminate the skyrmion in the above-described embodiment are as follows.

(11) When the direction of the skyrmion erasing pulse is the same as the direction of the generated pulse, the width Wm of the magnetic material size is 2λ>Wm> λ with respect to the skyrmion diameter λ.
It is. The height of the magnetic body size is also 2λ>hm> λ
It is.

  (12) When the direction of the skyrmion erasing pulse is the same as the direction of the generated pulse, the width W of the region A is 0.4 × λ. The height h is λ / 2. The gap d with the magnetic substance at the left end of the region A is 0.4 × λ> d> 0.2λ. If d is smaller than 0.2λ, skirmion can not be generated by the generated pulse.

  (13) The magnetic field intensity Ha of the skyrmion generation pulse applied to the region A follows the above generation condition (4). That is, Ha <0.015 J.

  (14) The magnetic field intensity Ha of the skyrmion erasing pulse applied to the region A is Ha <0.02 J.

Example 4
In Example 4, the simulation experiment result of the skyrmion erasing in case the area | region A is divided | segmented into two area | regions for production | generation A1 and erasure | elimination A2 is shown. FIG. 13C is a schematic view showing an example in which the region A is divided. The generation region A1 includes the end of the lower magnetic body 111. The erasing area A2 is adjacent to the generation area A1 on the opposite side of the end of the lower magnetic body 111 included in the generation area A1.

  The width W1 of the generation area A1 shown in FIG. 13C is 0.4 × λ, and the height h1 is 0.6 × λ. The width W2 of the erasing area A2 is 0.4 × λ and the height h2 is 0.4 × λ.

The width Wm of the magnetic body is in the following range with respect to the skyrmion diameter λ.
2λ>Wm> λ / 2
If Wm is too small, skill mions are not generated. Wm is preferably about λ.

The height hm of the magnetic body is in the following range with respect to the skyrmion diameter λ.
2λ>hm> λ / 2
If hm is too large, the skyrmion escapes from the current circuit and can not be erased when the skyrmion is erased.

  Skirmions can be generated by applying a generation pulse of the magnetic field intensity Ha1 to the two regions A1 and A2 shown in FIG. 13C. The skyrmion can be erased by applying the erasing pulse of the magnetic field intensity Ha2 to the area A2 different from the area A1. The generated pulse and the erasing pulse shown in FIG. 13A are pulsed magnetic fields having the same direction and the same magnitude as the magnetic field. In this example, the magnetic field strength Ha1 and the magnetic field strength Ha2 are 0.01 J. Thus, skill mions can be generated and eliminated. Further, FIG. 13B shows the case where the direction of the erasing pulse is the same as the direction of the generated pulse, and the magnetic field intensity Ha1 of the generated pulse is 0.01 J and the magnetic field intensity Ha2 of the erasing pulse is 0.015 J. . Even in this case, skill mions can be erased. If the magnetic field Ha of the region A2 is Ha <0.02 J, erasing is possible.

  When skirmion does not occur when the generation pulse is applied, skirmion is not generated by the applied magnetic field of the erasing pulse. This is because it is not possible to generate a skirmion because the height of the erasing area A2 is small.

  The conditions required to eliminate the skyrmion in the above-described embodiment are as follows.

  (15) In the case where the generation area A1 and the erasing area A2 are provided, generation and deletion of skirmions are possible even when the magnetic field strength Ha1 of the generated pulse and the magnetic field strength Ha2 of the erasing pulse are the same.

(16) The width Wm of the magnetic body is in the following range with respect to the skyrmion diameter λ.
2λ>Wm> λ / 2

(17) The height hm of the magnetic body is in the following range with respect to the skyrmion diameter λ.
2λ>hm> λ / 2

  As shown in FIG. 13B, the erase pulse may be smaller than the generation pulse, which is possible in the range of Ha2 <0.02 J. However, the skirmion can not be erased if the height of the erasing area A2 is 0.55 × λ or less.

  Thus, in the present embodiment, it has been shown that the generation and deletion of skillion is possible even when two different regions A1 and A2 are used for generation and deletion of skillion.

  In Example 1-4 mentioned above, the simulation experiment for skyrmion production and elimination by magnetic field application was shown. And, the design design rule for skyrmion generation and elimination was clarified in 17 items from (1) to (17).

  These 17 criteria are very important because they define basic rules for designing a skyrmion memory device. This design rule is expressed as a normalized quantity in two quantities, the magnetic exchange interaction J characterizing the magnetism of the magnetic substance and the generated skyrmion size λ. λ is related to the Jaroshinski-Moriya interaction D in [Equation 5]. In [Equation 5], a is the lattice constant of the magnetic body 11, D is the magnitude of the Jaroshinski-Moriya interaction, and is a physical constant unique to the substance. Therefore, the skyrmion diameter λ is a substance specific constant. As seen in Non-Patent Document 1, the skyrmion diameter λ is, for example, 70 nm for FeGe and 18 nm for MnSi.

  Therefore, this basic rule is expressed as a design rule applicable to various chiral magnetic materials, and the scope is wide.

  FIG. 14 and FIG. 15 are schematic views showing another example of the shape of the current circuit. FIG. 15 shows the case where the current circuit is in the form of a coil. The shape of the current circuit in the present invention is not limited to these shapes, and other similar current circuit shapes can be adopted.

  In addition, the conclusion in the embodiment of the chiral magnetic material described here does not qualitatively change the dipole magnetic material or the frustrated magnetic material.

  Thus, the present invention provides an optimal design guideline for the magnetic elements and the skyrmion memory that can generate and erase skyrmions.

  Since the design rules can be described in standardized quantities in the skyrmion size, common design guidelines can be given to various magnetic materials, and this will have a large impact on the practical application of magnetic elements using skyrmions. I can expect it.

  Skill-Mion memory can be written and erased many times. That is, there is no limitation on the number of times of writing and erasing, and the endurance (durability) is infinite.

  In addition, since skill mions exist stably, skill mions memory can greatly improve data retention (retention) performance.

  These two features of the magnetic element and the skyrmion memory according to the present invention solve all at once the problems such as the limitation of the number of times of writing of the electronic storage and the deterioration of the holding performance accompanying the case of the flash memory utilizing the insulating property of oxide film. It is a revolutionary thing.

  Skirmion is an ultrafine structure having a nanoscale size with a diameter of 1 to 100 nm, and can be applied as a large-capacity storage magnetic element capable of extremely densifying enormous bit information. The skyrmion memory can electrically write and erase. And the time required for this writing and erasing is also nanosecond. The use of such high-speed large-scale non-volatile memory significantly improves the high-speed processing capability of large-scale information required for many electronic devices at present.

  In addition, the skyrmion can write and erase directly by the magnetic field induced by the current while using the magnetic moment as a storage medium.

  By using the recording method by the current induced magnetic field of this skyrmion memory, it is possible to eliminate the mechanical drive part necessary for the hard disk which is a large capacity magnetic memory, greatly reducing the power consumption and degrading the drive parts such as wear parts. It also enables ultra-high-speed write and erase. For this reason, replacement of the current hard disk is possible.

  In addition, the flash memory has many advantages over flash memories that use electrical writing and erasing, whose recording capacity is increasing. Since the magnetic moment is used as a recording medium, the recording can be rewritten any number of times. In addition, the record retention time of Skill Mion memory is long.

  Due to these features, the use environment of a personal computer equipped with, for example, SkillMion memory is greatly improved. By using the skill-ion memory, shortening of the rise time from power-on to the device to operation becomes possible and speeding up of the response speed are realized, and a comfortable use environment is realized.

  In addition, it is possible to realize longer life of the mounted battery by power saving, and it is possible to realize more revolutionary specifications for mobile devices and the like.

  As long as CPU-equipped mobile phones and smart phones can use high-speed large-scale non-volatile memory using SkillMion, they can speed up image capture, execution of various application programs, image display, etc. Use environment is further improved.

  In addition, if the skill memory is mounted on a digital camera or a television receiver, it is possible to significantly increase the amount of data of a movie that can be stored.

  In addition, complex control processing, weather information processing, and a television receiver in a seat or a cabin are also used for self-propelled devices such as automobiles and flight devices such as aircraft by using skill memory for control devices and various mounted devices. It is possible to realize improvement of services for passengers by providing high quality images.

  Furthermore, by mounting the skyrmion memory according to the present invention to various devices such as control devices and experimental devices for space flight devices such as artificial satellites and aerospace vessels, a vast amount of information such as control information and information on observed images Can record and bring much knowledge to humanity.

  As described above, the skyrmion memory according to the present invention is a personal computer, data recording medium, data recording device, portable device incorporating a skyrmion memory-mounted CMOS-LSI device and skyrmion memory as high-speed large-scale nonvolatile memory. It can be mounted on many devices such as phones, smart phones, digital cameras, stick memories, communication devices, image recording devices, televisions, self-propelled devices, flight devices, space flight devices, etc. It can be expected to bring.

DESCRIPTION OF SYMBOLS 1 Magnetic shift register 2 Magnetic sensor 10 Magnetic element 12 Magnetic field generation part 111 Lower magnetic body 112 Current circuit S Skirmion

Claims (13)

It is a thin layer magnetic element capable of generating skyrmions,
A thin-layered lower magnetic material that becomes a skyrmion phase and a ferromagnetic phase according to the applied magnetic field strength ,
A predetermined area including an end portion of the lower magnetic body is provided on one surface side of the lower magnetic body so as to flow a current, whereby the first magnetic field applied to the lower magnetic body is directed in the opposite direction. A current circuit generating two magnetic fields in the predetermined area ;
A magnetic element comprising:   The current circuit is provided so as to surround the predetermined area in which the width W, which is the length in the spreading direction of the end of the predetermined area, is in the range of λ> W> λ / 4 with respect to the diameter λ of the skyrmion. The magnetic element according to claim 1, characterized in that:   In the current circuit, the height h, which is a length in the direction perpendicular to the spreading direction of the end of the predetermined area, is in the range of 2λ> h> λ / 2 with respect to the diameter λ of the skyrmion. The magnetic element according to claim 1 or 2, which is provided so as to surround the area.   The lower magnetic body has a notch formed at the end in the predetermined area, and a length L of a tangent between the notch and the predetermined area is in a range of λ> L> λ / 2. The magnetic element according to any one of claims 1 to 3, characterized in that: The lower magnetic body has a width Wm and a height hm, and the diameter λ of the generated skyrmion is
2λ>Wm> λ / 2
2λ>hm> λ / 2
Have a size that
Assuming that the width of the predetermined area is W and the height is h, the current circuit
λ ≧ W> λ / 4
2λ>h> λ / 2
The magnetic element according to any one of claims 1 to 4, wherein the magnetic element is provided so as to surround the predetermined area. The current circuit is provided on one surface side of the lower magnetic body so as to surround the predetermined region at a position deviated from the center of one end of the lower magnetic body.
Assuming that the lower magnetic body has a width of Wm and a height of hm, the diameter λ of the generated skyrmion is
2λ>Wm> λ
2λ>hm> λ
Have a size that
The current circuit has a width W of the predetermined area, a height h, and a width d of a gap between the current circuit and the other end adjacent to the one end of the lower magnetic body. Then,
W = 0.4 × λ
h = λ / 2
0.4 × λ>d> 0.2λ
The magnetic element according to any one of claims 1 to 4, wherein the magnetic element is provided so as to surround the predetermined area. The current circuit is provided on a surface side of the lower magnetic body so as to surround a first area including an end of the lower magnetic body and a second area adjacent to the first area opposite to the end.
The lower magnetic body has a width Wm and a height hm, and the diameter λ of the generated skyrmion is
2λ>Wm> λ / 2
2λ>hm> λ / 2
Have a size that
The first region surrounded by the current circuit has a width of 0.4 × λ parallel to the end, and a height 0.6 × λ perpendicular to the end.
The second region surrounded by the current circuit is characterized in that the width parallel to the end is 0.4 × λ and the height perpendicular to the end is 0.4 × λ. The magnetic element according to any one of claims 1 to 4, wherein The magnetic element according to any one of claims 1 to 7, wherein the lower magnetic body is made of any of a chiral magnetic body , a dipole magnetic body and a frustrated magnetic body . A magnetic element according to any one of claims 1 to 8 ;
And the applied possible magnetic field generating unit of the first magnetic field from a first direction to the magnetic element provided opposite to one surface of the magnetic element,
A power supply capable of applying a current for generating the second magnetic field to the current circuit;
Skyrmion memory, characterized in that to obtain Bei the. The power supply can apply a current to the current circuit of the magnetic element so as to generate a second magnetic field that is weaker than the first magnetic field and that is directed in the direction opposite to the first magnetic field. The skill mion memory according to claim 9 . 11. The skyrmion according to claim 9 , wherein the power supply can generate, for the current circuit, a generated pulse for generating the skyrmion and an erasing pulse for erasing the skyrmion. memory. 12. A CMOS-LSI device mounted with a skirmion memory, wherein the skyrmion memory according to any one of claims 9 to 11 and a CMOS-LSI device are formed in the same chip. An apparatus equipped with the skyrmion memory according to any one of claims 9 to 11 .

Images