JP6980318B2 - Spin accumulator - Google Patents

Description

The present invention relates to a spin storage device utilizing the characteristics of a superlattice layer having a topological insulating layer.

In recent years, research on spintronic devices has been actively conducted. The spintronics device refers to an electronic device in which an electric current is replaced with a spin current.
In order for the spintronics device to function, it is necessary to develop a spin battery (cell) and a spin source, which are compared with conventional batteries and power supplies, but a practical one has not been developed.

In connection with the spin battery (cell) and the spin source, a spin storage structure incorporated in the spintronics device has been reported (see, for example, Non-Patent Document 1).
An example of such a spin accumulation structure will be described with reference to FIG. Note that FIG. 7 is a cross-sectional view for explaining an example of a conventional spin accumulation structure.

As shown in FIG. 7, the spin storage device 100 includes a spin injection electrode 103 via a tunnel layer 102a formed of magnesium oxide or the like on a spin conduction layer 101 formed of a semiconductor or a metal thin film, and magnesium oxide or the like. The spin detection electrode 104 is arranged via the formed tunnel layer 102b.
The spin injection electrode 103 is made of a ferromagnetic material and injects an electric current to diffuse spin electrons into the spin conduction layer 101. The spin electrons diffused in the spin conduction layer 101 generate a magnetic resistance as a spin current with the spin detection electrode 104 also formed of a ferromagnetic material, which is detected as a spin signal.
In order to realize such a spin detection principle, in the spin injection electrode 103 and the spin detection electrode 104, it is necessary to interpose the tunnel layers 102a and 102b for moving the spin electrons between the spin injection electrode 103 and the spin conduction layer 101.

However, in the spin storage device 100, the amount of spin electrons diffused from the spin injection electrode 103 to the spin conduction layer 101 decreases exponentially as the distance from the spin injection electrode 103 increases, and the spin in a practically required short time is required. The electron propagation length L is less than 1 μm. Therefore, it is necessary to make the spin conduction layer 101, the tunnel layers 102a, 102b, the spin injection electrode 103, and the spin detection electrode 104 small in a remarkably limited region.
Further, if the spin conduction layer 101 is made small in accordance with the propagation length L of the spin electrons, the spin storage capacity is reduced, so that there is a problem that the function as the spin battery cannot be obtained.
Further, in order to solve these problems, it is assumed that graphene or the like having a long spin electron propagation length L is applied as a material for forming the spin conduction layer 101, but even if graphene or the like is used, the spin electron propagation length L is assumed. Is about 10 μm, and the function as the spin battery cannot be obtained, and operation at an extremely low temperature is required.
Further, since some spin electrons tunneled through the tunnel layers 102a and 102b are used for detection, the signal strength of the spin signal is weak and there is a problem in detection sensitivity.

Japanese Patent No. 5750791 Japanese Patent No. 6124320 Japanese Patent No. 6238495 International Publication No. 2016/147802

S. Maekawa, S. O. Valenzuela, E. Saitoh and T. Kimura, ed. “Spin Current,” Oxford Univ. Press, Oxford, UK, ISBN 978-0-19-960038-0, pp.227-243.

An object of the present invention is to solve the above-mentioned problems in the prior art and to achieve the following objects. That is, it is an object of the present invention to provide a spin storage device which is excellent in spin electron storage characteristics and supply characteristics and can operate at room temperature.

The present inventor has made diligent studies to solve the above problems and obtained the following findings.
That is, the present inventor is proceeding with research on a superlattice layer having a topological insulating layer for the accumulation of spin electrons (see Patent Documents 1 to 4). When the layer is used as a spin conduction layer, the propagation length L of spin electrons is extremely long, reaching the order of millimeters, and it is possible to store and supply (extract) spin electrons with good response in a short time at room temperature. I found it in.

The present invention is based on the above findings, and the means for solving the above-mentioned problems are as follows. That is,
<1> A substrate, a topological insulating layer arranged on the substrate and having a topological insulating property and being formed of an alloy material, and an electric insulating layer having an electrical insulating property and being formed of an alloy material different from the topological insulating layer. A super lattice layer that is repeatedly laminated alternately in this order, and a magnetic electrode that has at least one linear portion that is arranged on the super lattice layer and is bridged between two outer edges of the surface of the super lattice layer. , A spin accumulator characterized by having.
<2> The spin accumulator according to <1>, wherein the magnetic electrode is made of a magnetic material capable of magnetizing in a direction parallel to either the in-plane direction or the perpendicular direction of the superlattice layer.
<3> From <1> to <1>, the magnetic electrode has one linear portion, and the surface area of the superlattice layer is divided into two regions with the linear portion as a boundary line. 2> The spin accumulator according to any one of.
<4> It has a plurality of linear portions having either the same shape or a similar shape, and one said linear portion is arranged in parallel with another adjacent said linear portion and the other said linear portion. The spin electrons of one polarity are accumulated in the three or more regions defined by the linear portion and the outer edge of the surface of the superlattice layer, which are capable of conducting a current in the opposite direction to the above. The spin according to any one of <1> to <2>, wherein the linear portion is arranged so that the total surface area of the region and the total surface area of the region where the spin electrons of other polarities are accumulated are different. Storage device.
<5> The spin accumulator according to <4>, wherein the magnetic electrode has a structure in which a linear magnetic material is folded back and bent to have a plurality of linear portions.
<6> The spin accumulator according to any one of <1> to <5>, wherein the topological insulating layer contains at least one of Sb, Bi, Se, and Te.
<7> The spin accumulator according to any one of <1> to <6>, wherein the electrically insulating layer contains at least one of Si, Ge, Sn, Se, and Te and has the property that the spatial inversion symmetry is broken. ..
<8> The property that the topological insulating layer contains at least one of Sb, Bi, Se, and Te, the electrically insulating layer contains at least one of Si, Ge, Sn, Se, and Te, and the spatial inversion symmetry is broken. When each layer of the topological insulating layer and the electrical insulating layer is counted as one layer, the number of superlattice layers stacked is 10 to 50, whichever is from <1> to <7>. The spin accumulator according to the description.
<9> The above <1> to <8>, wherein the substrate is either an insulating substrate exhibiting electrical insulation or an insulating processed substrate in which at least the surface region on which the superlattice layer is arranged is formed of the insulating material exhibiting electrical insulation. > The spin accumulator according to any one of.
<10> The spin storage device according to any one of <1> to <9>, to which an extraction electrode capable of extracting spin electrons accumulated in the superlattice layer is attached.

According to the present invention, it is possible to solve the above-mentioned problems in the prior art, to provide a spin storage device having excellent spin electron storage characteristics and supply characteristics and capable of operating at room temperature.

It is explanatory drawing which shows the example of the crystal structure of the topological insulating layer which is a hexagonal crystal. It is explanatory drawing which shows the example of the crystal structure of the said electric insulation layer which is a cubic crystal. It is a top view for demonstrating the structure of the spin accumulator 1 which concerns on 1st Embodiment. FIG. 2 is a cross-sectional view taken along the line AA'in FIG. 2A. It is explanatory drawing for demonstrating the modification about the extraction of a spin electron. It is explanatory drawing which shows the schematic structure of the spin accumulator which concerns on 2nd Embodiment. It is explanatory drawing which shows the schematic structure of the spin accumulator which concerns on 3rd Embodiment. It is explanatory drawing which shows the schematic structure of the spin accumulator which concerns on 4th Embodiment. It is explanatory drawing which shows the operation state of the spin accumulator which concerns on 4th Embodiment. It is sectional drawing for demonstrating the example of the conventional spin accumulation structure.

(Spin storage device)
The spin accumulator of the present invention has a substrate, a superlattice layer, and a magnetic electrode, and may have other members, if necessary.

<Board>
The substrate is not particularly limited, and a known substrate can be used.
Of these, a non-magnetic substrate made of a non-magnetic material that is not easily affected by an external magnetic field is preferable.
Further, in order to suppress the generation of leakage current from the super lattice layer, an insulating substrate exhibiting electrical insulation and at least a surface region on which the super lattice layer is arranged are made of an insulating material exhibiting electrical insulation. Substrates are preferred.
Examples of the substrate having the characteristics of the non-magnetic substrate and the insulating substrate include a glass substrate and a sapphire substrate.

Further, as the substrate, it is preferable that the orientation control layer is formed in the surface region where the superlattice layer is arranged as the base layer for forming the superlattice layer.
The orientation control layer is not particularly limited, but any of germanium, silicon, tungsten, germanium-silicon, germanium-tungsten, and silicon-tungene can be easily obtained because the crystal orientation of the superlattice layer to be laminated can be easily obtained. It is preferable to include the above, and it may be composed of either crystalline or amorphous.
The thickness of the orientation control layer is not particularly limited, but is preferably 1 nm to 100 nm, and more preferably 10 nm to 50 nm.
If the thickness is less than 1 nm, it becomes difficult to control the orientation of the superlattice layer, and if it exceeds 100 nm, the surface unevenness becomes large and the orientation control may become difficult.
The method for forming the orientation control layer is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a sputtering method, a vacuum deposition method, a molecular beam epitaxy method, an ALD (Atomic Layer Deposition) method, CVD ( Chemical Vapor Deposition) method and the like can be mentioned.

<Superlattice layer>
The superlattice layer is a layer arranged on the substrate and in which topological insulating layers and electrical insulating layers are alternately and repeatedly laminated in this order.

-Topological insulator layer-
The topological insulating layer is a layer that exhibits topological insulating properties and is formed of an alloy material.
In addition, in this specification, "topological insulation" means the property that it becomes a conductor at the surface or the interface of a layer, but becomes an insulator inside the layer. Further, the topological insulating layer exhibiting the topological insulating property has spatial inversion symmetry.

The topological insulating layer is not particularly limited, but is preferably formed by containing at least one of Sb, Bi, Se and Te.
Among them, it is preferable that the layer is formed mainly of any one of _{SbTe, Sb 2} Te ₃ , BiTe, Bi ₂ Te ₃ , BiSe and Bi ₂ Se _{3 and is oriented in a certain crystal orientation.}
In addition, in this specification, a "principal component" indicates an element forming a basic unit cell of a layer.
The topological insulating layer is not particularly limited, but preferably has a hexagonal crystal structure and its c-axis is oriented in the stacking direction.
Having such a crystal structure makes it easy to obtain a superlattice structure composed of these layers by using the layer to be laminated next as a template for producing orientation using this layer as a base.

The method for forming the topological insulating layer is not particularly limited, but since the crystal structure oriented in the c-axis can be easily obtained, for example, a sputtering method, a vacuum vapor deposition method, a molecular beam epitaxy method, an ALD method, a CVD method, etc. Is preferable.
The thickness of the topological insulating layer is not particularly limited, but is preferably 1.0 nm to 5.0 nm from the viewpoint of preferably obtaining the topological insulating property.

-Electrical insulation layer-
The electrically insulating layer is a layer that exhibits electrical insulation and is formed of an alloy material different from that of the topological insulating layer.

The electrically insulating layer is not particularly limited, but preferably contains at least one of Si, Ge, Sn, Se, and Te and has a property that the spatial inversion symmetry is broken. With this configuration, it is possible to facilitate conducting the spin current accompanying the cleavage of the spin band.
Above all, it is preferable that the electrically insulating layer is formed mainly of an alloy (for example, GeTe) having a composition of Se and Te, which are chalcogen atoms, and a composition of Ge of 1 or less.
Further, the electrically insulating layer is preferably a layer oriented in a certain crystal orientation. With this configuration, the layer can have a common crystal axis with the topological insulating layer whose orientation is controlled.

The electrically insulating layer is not particularly limited, but preferably has a cubic crystal structure and its (111) plane is laminated on the adjacent plane of the topological insulating layer. Above all, it is more preferable that the face-centered cubic crystal structure is formed and the (111) plane thereof is laminated on the adjacent plane of the topological insulating layer.
Having such a crystal structure makes it easy to obtain a superlattice structure composed of these layers by using the layer to be laminated next as a template for producing orientation using this layer as a base.
The method for forming the electrically insulating layer is not particularly limited, but since the crystal structure oriented in the c-axis can be easily obtained, for example, a sputtering method, a vacuum vapor deposition method, a molecular beam epitaxy method, an ALD method, a CVD method, etc. Is preferable.
The thickness of the electrically insulating layer is not particularly limited, but is preferably 0.3 nm to 4.0 nm, and more preferably 0.4 nm to 1.0 nm.
If the thickness is less than 0.3 nm, it is difficult to form, and if it exceeds 4 nm, it may exhibit independent and unique properties.

Here, the laminated state of the topological insulating layer and the electrical insulating layer will be described with reference to FIGS. 1 (a) and 1 (b). Note that FIG. 1A is an explanatory diagram showing an example of the crystal structure of the topological insulating layer which is hexagonal, and FIG. 1B is an example of the crystal structure of the electrically insulating layer which is cubic. It is explanatory drawing which shows.

As shown in FIG. 1A, when the hexagonal crystal alignment layer 51 is c-axis oriented as the topological insulating layer, the adjacent surface 51a becomes hexagonal. Therefore, when the crystal alignment layer 52, which is a cubic crystal, is deposited on the surface of the crystal alignment layer 51 as the electrical insulating layer, the (111) plane shown in FIG. 1 (b) becomes the adjacent plane 52a. That is, since the (111) plane of the cubic crystal is triangular, it matches the adjacent plane 52a of the crystal orientation layer 51 oriented with the c-axis. Therefore, when the crystal alignment layer 52 which is a cubic crystal is deposited on the surface of the crystal alignment layer 51 aligned with the c-axis, the adjacent planes 52a thereof can be used as the (111) plane of the crystal alignment layer 52. On the other hand, when the crystal alignment layer 52 is formed without the crystal alignment layer 51, the crystal alignment layer 52 is oriented to, for example, the (100) plane, and as a result, the superlattice formed by these laminates is formed. The structure is prone to lattice disturbance.

The number of laminated superlattice layers is not particularly limited, but the topological insulating layer contains at least one of Sb, Bi, Se and Te, and the electrical insulating layer is Si, Ge, Sn, Se and Te. When at least one of them is contained and the spatial inversion symmetry is broken, the number of layers is preferably 10 to 50, preferably 10 to 50, when each layer of the topological insulating layer and the electrically insulating layer is counted as one layer. It is particularly preferable that the number is about a layer.
If the number of layers is less than 10, the amount of spin accumulation may be insufficient, and if it exceeds 50 layers, the orientation of the layers on the surface layer side tends to be disturbed, but more layers are laminated. However, the effect of improving the spin accumulation amount may not be expected due to the saturation of the spin accumulation amount.
The outermost layer of the superlattice layer is not particularly limited, but is composed of an antioxidant layer formed in the same manner as the topological insulating layer in order to suppress oxidation of the electrical insulating layer on the surface layer side. Is preferable.

<Magnetic electrode>
The magnetic electrode has at least one linear portion arranged on the superlattice layer and bridged between two outer edges of the surface of the superlattice layer.

The magnetic material for forming the magnetic electrode is not particularly limited, and examples thereof include a ferromagnetic material used as a magnetic layer forming material for a known magnetic memory.
Above all, a magnetic material that can be magnetized in a direction parallel to either the in-plane direction or the in-plane direction of the superlattice layer is preferable. When the magnetic electrode is formed of such a magnetic material, it is possible to simplify the wiring design of the linear portion for the operation of accumulating and supplying (extracting) spin electrons.
Specific examples of the magnetic material that can be magnetized in the direction parallel to the in-plane direction of the superlattice layer include permalloy alloys and the like.
Moreover, as a specific magnetic material which can be magnetized in the direction parallel to the plane direction of the superlattice layer, TbFeCo and the like can be mentioned.
The method for forming the magnetic electrode is not particularly limited, and examples thereof include a known microfabrication method using a mask.

The wiring configuration of the magnetic electrode is not particularly limited, but when the magnetic electrode has one linear portion, the surface area of the superlattice layer is divided into two with the linear portion as a boundary line. It is preferable to arrange the linear portions so that the surface areas of the regions are different from each other.
With such a wiring configuration, the polarity of the spin electrons accumulated on the larger surface area becomes dominant in one region where spin electrons having different polarities are diffused and the other region, and by extension, the spin electrons It can be effectively stored and supplied (taken out).

Further, when the number of the linear portions is plurality, the linear portions have a plurality of shapes having the same shape or a similar shape, and one linear portion is in parallel with another adjacent linear portion. One of three or more regions arranged and capable of conducting a current in the direction opposite to that of the other linear portion and defined by the linear portion and the outer edge of the surface of the superlattice layer. The linear portion is arranged so that the total surface area of the region where the spin electrons of the same polarity are accumulated and the total surface area of the region where the spin electrons of other polarities are accumulated are different. Is preferable.
With such a wiring configuration, since the linear portion as a spin supply source is densely arranged on the superlattice layer, the amount of spin electrons diffused and accumulated in the superlattice layer is increased. be able to.

Further, when the number of the linear portions is plurality, it is preferable that the magnetic electrode is configured to have the plurality of linear portions by folding back and bending the linear magnetic material.
With such a wiring configuration, it is not necessary to connect a power supply for each of the linear portions, and a simple configuration can be achieved.

<Other parts>
The other members are not particularly limited as long as the effects of the present invention are not impaired, and examples thereof include a take-out electrode.
The extraction electrode is an electrode capable of extracting spin electrons accumulated in the superlattice layer.
The material for forming the take-out electrode is not particularly limited, and can be appropriately selected from known electrode materials.
The method for forming the take-out electrode is not particularly limited, and examples thereof include a known microfabrication method using a mask.

In addition, in order to take out the spin electrons accumulated in the spin accumulator, it is not always necessary to arrange the take-out electrode, and it is taken out by contacting an external spin detector or formed at each end of the magnetic electrode. A wire having high spin conductivity may be short-circuited to the electrical connection portion to be taken out.

An example of an embodiment of the present invention will be described in more detail with reference to the drawings.
First, the spin accumulator 1 according to the first embodiment of the present invention will be described with reference to FIGS. 2 (a) to 2 (c). Note that FIG. 2A is a top view for explaining the configuration of the spin storage device 1 according to the first embodiment, and FIG. 2B is a line AA'in FIG. 2A. It is a cross-sectional view, and FIG. 2C is an explanatory diagram for explaining a modification of the extraction of spin electrons.

As shown in FIG. 2A, the spin storage device 1 mainly has a substrate 2, a superlattice layer 4 arranged on the substrate 2, and a magnetic electrode 5 arranged on the superlattice layer 4. ..

The superlattice layer 4 is formed of a crystallized alloy layer, and as shown in FIG. 2B, is formed with an orientation control layer 3 for controlling the crystal orientation of the alloy layer as a base.
With the orientation control layer 3 as a base, the topological insulating layer 4a and the electrical insulating layer 4b are alternately and repeatedly laminated in this order to form the superlattice layer 4.
A topological insulating layer 4a that also serves as an antioxidant layer is formed on the outermost layer of the superlattice layer 4 in order to prevent oxidation of the electrical insulating layer 4b on the outermost surface side.

The magnetic electrode 5 has a linear portion 5a straddled between two outer edges of the surface of the superlattice layer 4 and two electrical connection portions 5b formed at each end position of the linear portion 5a.
The linear portion 5a, so as to have different surface areas in the region R _1, R ₂ mutually surface region of the superlattice layer 4 when viewed is divided linear portion 5a in two as a boundary line FIGS. 2 (a) It is arranged in the middle and to the right of the superlattice layer 4.
Further, the magnetic electrode 5 is formed of a magnetic material that can be magnetized in a direction parallel to the in-plane direction of the superlattice layer 4.

Further, in the spin storage device 1 of this example, a take-out electrode 8 formed of an electrode material is attached as an accessory portion.
The extraction electrode 8 is arranged on the superlattice layer 4, and has a wiring 8a extending in a direction parallel to the linear portion 5a of the magnetic electrode 5 and two terminal portions 8b formed at each end position of the wiring 8a. And have.

The operation of the spin storage device 1 configured in this way will be described.
First, an external magnetic field B is applied in a direction parallel to the in-plane direction of the superlattice layer 4 to magnetize the magnetic electrode 5.
Each electric connection portion 5b of the magnetic electrode 5 is short-circuited by the electric wiring 6 to supply electric power from the power source 7 to conduct the current i to the magnetic electrode 5.
Then, a spin current js is generated in a direction orthogonal to the direction of the current i flowing in the linear portion 5a, and the spin electrons in the magnetic electrode 5 are diffused in the superlattice layer 4. In this case, spin electrons, the linear portion 5a was split into two as a boundary region R _1, R ₂ and with different polarities spin electrons (up-spin electrons, down-spin electrons) are diffused by the spin current js The Rukoto. In this example, the downspin electrons are diffused to the right side in the traveling direction of the current i, and the upspin electrons are diffused to the left side in the traveling direction of the current i.
The spin electrons diffused in the superlattice layer 4 are accumulated in the superlattice layer 4 as they are. The polarity of the accumulated spin electrons is determined by the capacitance difference of the superlattice layer 4, that is, the difference in the surface area of _{the regions R 1} and R _{2 divided into two with the linear portion 5a as the boundary line, and is determined from the region R 1} . up-spin electrons was also spread on a large surface area region R ₂ is dominant.
The propagation length L of spin electrons diffused and accumulated in the superlattice layer 4 under a practical time constraint is extremely long and reaches the order of millimeters. If the wiring 8a of the extraction electrode 8 is within the propagation length L of the spin electrons, the spin electrons reach the wiring 8a due to the spin current js.
Then, in the extraction electrode 8, a potential difference is generated in the direction orthogonal to the spin current js, and by short-circuiting between the two terminal portions 8b, a current amplified by the accumulated spin electrons flows.
That is, the spin storage device 1 can generate spin electrons as a spin source, can store spin electrons as a spin battery (cell), and supplies the stored spin electrons to an external spintronics device. can do.
In addition, in the spin storage device 1, the superlattice layer 4 having excellent spin electron propagation responsiveness has good spin electron storage and supply responsiveness, and the spin storage capacity is large according to the size of the superlattice layer 4. It can be made into a capacity.

Regarding the spin storage device 1, in the example shown in FIGS. 2 (a) and 2 (b), the take-out electrode 8 is arranged, but in the spin storage device 1, instead of the take-out electrode 8 for taking out spin electrons, an external electrode 8 is arranged. The spin detector 10 of the above can also be used. FIG. 2 (c) shows a configuration example of a spin storage device using a spin detector.
As shown in FIG. 2 (c), the spin detector 10 is composed of a U-shaped superlattice line 11 and an electrode line 12 arranged in a direction orthogonal to the bottom line of the superlattice line 11.
The U-shaped superlattice line 11 is composed of a superlattice and can be formed in the same manner as the superlattice layer 4. Further, the electrode wire 12 is made of an electrode material.
Now, when the ends E and F of the U-shaped superlattice line 11 are brought into contact with the positions C and D on the surface of the superlattice layer 4 in a state where the current i is conducted to the magnetic electrode 5, the inside of the superlattice layer 4 is formed. Diffused and accumulated spin electrons flow into the superlattice line 11.
Then, a potential difference is generated between the ends G and H of the electrode wire 12, and the current based on the spin electrons can be taken out by short-circuiting the ends G and H.

Next, the spin storage device 20 according to the second embodiment of the present invention will be described with reference to FIG. Note that FIG. 3 is an explanatory diagram showing a schematic configuration of the spin storage device according to the second embodiment.
As shown in FIG. 3, the spin storage device 20 mainly includes a substrate 22, a superlattice layer 24, and a magnetic electrode 25, and excludes the magnetic electrode 25, the substrate 22, the superlattice layer 24, and others. The unit is formed with the same configuration as that described for the spin storage device 1 according to the first embodiment.
The magnetic electrode 25 has a linear portion 25a and an electrical connection portion 25b, and the linear portion 25a has a bent linear shape unlike the linear portion 5a of the magnetic electrode 1 of the spin storage device 1.
Even in such a configuration, spin electrons having different polarities on the right side and the left side in the traveling direction of the current flowing between the two electrical connection portions 25b are diffused in the superlattice layer 24, and the linear portion 25a is used as a boundary line. region R ₃ of the superlattice layer 24 that is _divided, R ₄ and a different polarity of the spin electrons is to be accumulated.
In this example, the linear portion 25a has a curved linear shape, but the same effect can be obtained even when the linear portion 25a has a curved linear shape as a modified example.

Next, the spin storage device 30 according to the third embodiment of the present invention will be described with reference to FIG. Note that FIG. 4 is an explanatory diagram showing a schematic configuration of the spin storage device according to the third embodiment.
As shown in FIG. 4, the spin storage device 30 is mainly composed of a substrate 32, a superlattice layer 34, and two magnetic electrodes 35, 35', and the substrate 32, the superlattice layer 34, and individual magnetism. The electrodes 35, 35'and other parts are formed with the same configuration as that described for the spin accumulator 1 according to the first embodiment.
In the spin storage device 30, unlike the spin storage device 1, two magnetic electrodes 35 and 35'are arranged.
The two magnetic electrodes 35, 35'have linear portions 35a, 35a'of the same shape, the linear portions 35a are arranged in parallel with the adjacent linear portions 35a', and the linear portions 35a, 35a are arranged in parallel. 'and of the three regions R ₄ to R ₆ that is defined by the outer edges of the superlattice layer surface, and the surface area of the region R ₅ where one polar spin electrons are accumulated, the spin electrons of other polar accumulation the region to _R 4, the total surface area differently linear portion 35a of the _{R 6,} 35a 'is disposed.

Now, the two electrical connection portions 35b of the magnetic electrode 35 are connected to the first power supply to pass a current through the linear portion 35a, and the two electrical connection portions 35b'of the magnetic electrode 35'are connected to the second power supply to form a wire. When a current in the direction opposite to that of the linear portion 35a is passed through the shaped portion 35a', spin electrons of one polarity are diffused on the right side in the traveling direction of each current, and spin electrons of another polarity are diffused on the left side in the traveling direction.
Accordingly, spin-spin electrons of the same polarity in the region R ₄ and region R ₆ of the superlattice layer 34 is diffused, is accumulated, in the region R ₅ of the superlattice layer 34, the diffusion in the region R ₄ and region R _6, it is accumulated Spin electrons with different polarities from the electrons will be diffused and accumulated.
In such a spin storage device 30, since the magnetic electrodes 35 and 35'as spin supply sources are densely arranged on the superlattice layer 34, the amount of spin electrons diffused and accumulated in the superlattice layer 34. Can be increased.
In this example, the magnetic electrode has two linear portions 35a and 35a', but it may have three or more linear portions.

Next, the spin storage device 40 according to the fourth embodiment of the present invention will be described with reference to FIG. Note that FIG. 5 is an explanatory diagram showing a schematic configuration of the spin storage device according to the fourth embodiment.
As shown in FIG. 5, the spin storage device 40 is mainly composed of a substrate 42, a superlattice layer 44, and a magnetic electrode 45, and the substrate 42 excluding the magnetic electrode 45, the superlattice layer 44, and other parts. Is formed with the same configuration as that described with respect to the spin accumulator 30 according to the third embodiment.
Unlike the spin accumulator 30, the spin accumulator 40 has _{four linear portions 45a 1 to} 45a 4 having the same shape, and each of the linear portions 45a _{1 to 45a 4} is adjacent to the other. It is arranged in parallel with the linear portion and can conduct current in the opposite direction to other adjacent linear portions, and is defined by the _{linear portions 45a 1 to 45a 4} and the outer edge of the surface of the super lattice layer 44. Of the five regions R _{7 to} R ₁₁ , the total surface area of regions R ₇ , R ₉ , and R ₁₁ where spin electrons of one polarity are accumulated, and the region R _{8 where spin electrons of other polarities are accumulated.} , The _{linear portions 45a 1 to 45a 4} are arranged so as to be different from the total surface area of _{R 10.}
Further, in the spin storage device 40, unlike the spin storage device 30, one linear magnetic material is used so that adjacent linear portions are connected to each other at the end positions on the end side or the start end side in the traveling direction of the electric current. It has a structure that is folded back and bent at the outer peripheral position of the superlattice layer 44.

Now, when the two electrical connection portions 45b of the magnetic electrode 45 are connected to a power source and a _{current is passed through the linear portions 45a 1 to 45a 4} , spin electrons of one polarity are diffused to the right side in the traveling direction of the current, and the traveling direction. Spin electrons of other polarities are diffused on the left side.
Therefore, spin electrons of the same polarity are diffused in the regions R ₇ , R ₉ and R ₁₁ of the superlattice layer 44, and diffused in the regions R ₈ and R ₁₀ of the superlattice layer 44 and in the regions R ₇ , R ₉ and R ₁₁ . , Spin electrons with different polarities from the accumulated spin electrons will be diffused.

The operating state of the spin accumulator according to the fourth embodiment will be described with reference to FIG. Note that FIG. 6 is an explanatory diagram showing an operating state of the spin accumulator according to the fourth embodiment.
As shown in FIG. 6, when the two electrical connection portions 45b of the magnetic electrode 45 are connected to the power supply 47 via the electrical wiring 46 and a current i is passed, the magnetic electrode magnetized by the application of the magnetic field from the external magnetic field B. A spin current is generated from 45 in a direction orthogonal to the current i, and spin electrons are diffused from the magnetic electrode 45 into the superlattice layer 44.
Assuming that the downspin electrons are diffused to the right side in the traveling direction of the current i and the upspin electrons are diffused to the left side in the traveling direction, the upspin electrons are diffused in the regions R ₇ , R ₉ , and R ₁₁ of the superlattice layer 44. Downspin electrons are diffused in _{the regions R 8} and R ₁₀ of the super lattice layer 44.
_{Here, the linear portions 45a 1 to 45a 4} are formed so that the total surface area of the regions R ₇ , R ₉ and R _{11 and} the total surface area of the regions R ₈ and R _{10 where spin electrons of other polarities are accumulated are different.} Since the total surface area of the regions R ₇ , R ₉ , and R ₁₁ is set to be larger than the total surface area of the regions R ₈ and R ₁₀ , the upspin electrons diffused in _{the regions R 7} , R ₉ , and R _{11 are arranged.} The accumulated amount of is dominant.
With the current i conducted to the magnetic electrode 45, the ends E and F of the U-shaped superlattice line 11 of the spin detector (see FIG. 2C) described in the first embodiment are superlatticed. When it comes into contact with the positions C and D on the surface of the layer 44, the spin electrons diffused and accumulated in the superlattice layer 44 flow into the superlattice line 11 and short-circuit between the ends G and H of the electrode wire 12. The current based on the spin electrons can be taken out.

In the spin storage device 40 configured as described above, since the linear portions 45a _{1 to 45a 4} of the magnetic electrode 45 as the spin supply source are densely arranged on the superlattice layer 44, the linear portions 45a 1 to 45a 4 are densely arranged in the superlattice layer 44. The amount of spin electrons diffused and accumulated can be increased.
In addition, in the spin accumulator 40, since the magnetic electrode 45 has a structure in which the linear magnetic material is folded back and bent to have a plurality of linear portions 45a _{1 to 45a 4} , the spin accumulator 40 is like the spin accumulator 30. It is not necessary to connect a power source (first power source, second power source) for each of the three linear portions, and the configuration can be simplified.

(Example 1)
The spin storage device 1 according to the first embodiment was manufactured according to the configuration of the spin storage device 1 shown in FIG. 2 (c). The specific manufacturing conditions are as follows.
First, a non-magnetic sapphire substrate (manufactured by Shinko Co., Ltd.) having a thickness of 280 μm as the substrate 2 was transferred to a sputtering device (manufactured by Shibaura Mechatronics Co., Ltd., equipped with three 4EP-LL, 3-inch targets), and the vacuum back pressure was 1.0. Sputtering was performed using a silicon material (manufactured by Mitsubishi Materials, B-doped Si) as a target under the conditions of × 10 ^-4 Pa, temperature of 25 ° C., and RF power of 100 W, and the base layer was placed on the non-magnetic sapphire substrate. The amorphous silicon layer as No. 3 was formed with a thickness of 30 nm.
Next, the non-magnetic sapphire substrate in this state was taken out from the sputtering apparatus, covered with a CuNi metal stencil mask (Meltech, 70 μm thick) having a window of 3 mm in length × 15 mm in width, and then again. It was transferred to the sputtering apparatus.
Next, after waiting for the vacuum back pressure to reach 1.0 × 10 ^-4 Pa, surface cleaning was performed with an RF power of 100 W to sufficiently remove the surface oxide film on the non-magnetic sapphire substrate.
_{Next, sputtering was performed using an Sb 2} Te ₃ alloy material (manufactured by Mitsubishi Materials, 99.9% purity) as a target under the conditions that the vacuum back pressure was maintained, the temperature was 25 ° C., and the RF power was 20 W. _{An Sb 2} Te ₃ alloy layer (first layer) as the topological insulating layer 4a was formed on the amorphous silicon layer through a window of a metal stencil mask to a thickness of 3.0 nm. After formation, the mixture was heated at 210 ° C. to crystallize the _{Sb 2} Te _{3 alloy layer.}
Next, while maintaining the vacuum back pressure and maintaining the temperature at 210 ° C., sputtering was performed using a GeTe alloy material (manufactured by Mitsubishi Materials Corporation, purity 99.9%) as a target under the condition that the RF power was 20 W. A GeTe alloy layer (first layer) as an electrically insulating layer 4b was formed on the _{Sb 2} Te ₃ alloy layer through the window of the metal stencil mask to a thickness of 0.8 nm and crystallized.
Next, except that the thickness condition was changed from 3.0 nm to 1.0 nm, the Sb ₂ Te ₃ alloy layer of the second and subsequent layers was formed under the same conditions as the first layer, and the thickness condition ( 0.8 nm), including forming the GeTe alloy layer of the second and subsequent layers in the same conditions as the first layer, and the _Sb 2 Te ₃ alloy layer and the GeTe alloy layer is laminated by six layers alternately , A superlattice layer (superlattice layer 4) having a laminated structure of 12 layers in total was produced.
The one layer on the GeTe alloy layer, which is the outermost layer of the superlattice layer, except that the thickness condition was changed from 3.0 nm to 4.0 nm in order to prevent oxidation of the GeTe alloy layer. _{The Sb 2} Te ₃ alloy layer (antioxidant layer) formed under the same conditions as the eyes is formed.
Next, after cooling the non-magnetic sapphire substrate in this state to room temperature, the metal stencil mask was taken out from the sputtering apparatus, and the metal stencil mask was opened with a window of 5 mm in length × 100 μm in width. It was replaced with 70 μm). At this time, the electrode forming a stencil mask, the magnetism electrode wire as the linear portion 5a of the surface area of the superlattice layer _{1: 2 (R 1: R} 2, R 1, the _{R 2} FIG 2 (c) It was covered so as to be divided by the area ratio of (see).
The non-magnetic sapphire substrate in this state is transferred to the sputtering device again to perform vacuuming ^{, and after waiting for the vacuum back pressure to reach 1.0 × 10 -4} Pa, the temperature is 25 ° C. and the RF power is 100 W. Sputtering was performed using a permalloy alloy material (manufactured by Mitsubishi Materials Corporation, purity 99.9%, Ni80at% Fe20at%) as a target to form the magnetic electrode wire with a thickness of 40 nm.
As described above, the spin accumulator according to Example 1 was manufactured.

A confirmation test of spin accumulation was performed on the spin accumulation device according to Example 1.
For the detection of spin electrons, the spin detector 10 described with reference to FIG. 2 (c) is used. Specifically, the U-shaped superlattice line 11 has a laminated structure similar to that of the superlattice layer, and the platinum electrode wire 12 arranged in a direction orthogonal to the bottom line of the superlattice line 11 is formed with a thickness of 40 nm. Was used. The distance between the terminals EF of the superlattice wire 11 is 1.0 mm.
When the spin detector 10 comes into contact with the superlattice layer in which spin electrons are accumulated, a spin current flows into the superlattice line 11 and between the ends G and H of the platinum electrode 12 due to the reverse spin Hall effect. Causes a potential difference in. Therefore, by connecting the ends G and H to a voltmeter and detecting the voltage of the normal current flowing between the ends G and H, the presence and amount of spin electrons accumulated in the superlattice layer can be determined. Detected.
Further, in the detection method using the spin detector 10, since the accumulated upspin electrons and downspin electrons cancel each other out as a pair, the current based on the spin electrons that are not canceled is detected.

In the confirmation test, first, with respect to the spin accumulator according to the first embodiment, 0.5 T in a direction parallel to the extending direction of the magnetic electrode wire as the linear portion 5a (see B in FIG. 2C). The magnetic field of the above was applied to magnetize the magnetic electrode.
Then, a DC current of 1.0 mA was passed between the magnetic electrode wires for 5 minutes.
Next, the terminals E and F of the spin detector 10 are placed at positions C and D on the surface of the superlattice layer of the spin accumulator according to the first embodiment so as to straddle the magnetic electrode wire at an intermediate position between the terminals E and F. Made contact with.
Then, the voltmeter indicated a voltage having a value of 140 μV to 150 μV.
Further, when the energization of the 1.0 mA current flowing between the magnetic electrode wires was instantaneously stopped, the indicated value of the voltmeter became 0 V within a few seconds.
From these facts, it is confirmed that in the spin accumulator according to the first embodiment, spin electrons are diffused and accumulated in a short time. In addition, the magnetic electrode wire as the linear portion 5a divides the surface area of the superlattice layer by an area ratio of 1: 2 (see FIG. 2 (c) for _{R 1} : R ₂ , regions R ₁ and R _2). with the provided is possible to, the difference in accumulation has occurred between the up-spin electrons and down-spin electrons, the larger side of the region of the surface area in (region R _2, see FIG. 2 (c)), small side area surface area spin electrons to a distance greater than the width of the (regions R _1, see FIG. 2 (c)) is spread, it is being confirmed that accumulated. Furthermore, it is confirmed that the accumulated spin electrons can be taken out to the outside in a short time.

(Reference Example 1)
Wherein the arrangement of the electrodes for forming a stencil mask, the area ratio of the surface area of the superlattice layer which is divided by the magnetic electrode wire as the linear portion 5a _{(R 1:} R _2, the region R _1, R ₂ 2 (c) a reference) 1: 2 to 1: was changed to 1, to prepare a spin accumulation device according to reference example 1 in the same manner as in example 1.
To spin accumulation device according to Reference Example 1, in an identical manner with respect to the spin accumulation device according to Embodiment 1 was subjected to a confirmation test spin accumulation, indication of the voltmeter using spin detector 10 The value was about 1 μV or less.
From comparison with confirmation tests this as for Example 1, the area ratio of the surface area of the magnetic electrodes two of said superlattice layer divided by _lines: a (R 1 _{R 2)} 1: based on 1 was that It is presumed that upspin electrons and downspin electrons were generated in the super lattice layer in almost the same amount with the wiring position of the magnetic electrode wire as a boundary line.

(Comparative Example 1)
Instead of the superlattice layer, a single Sb ₂ Te ₃ alloy layer having a thickness of 15 nm was formed by the same forming method as that of the _{Sb 2} Te _{3 alloy layer of the superlattice layer.} The spin accumulator according to Comparative Example 1 was produced in the same manner as in Example 1.

(Comparative Example 2)
Instead of the superlattice layer, a single GeTe alloy layer having a crystal orientation of <111> and a thickness of 15 nm was formed according to the method for forming the GeTe alloy layer of the superlattice layer. Except for this, the spin accumulator according to Comparative Example 2 was produced in the same manner as in Example 1.

(Comparative Example 3)
The spin accumulator according to Comparative Example 3 was produced in the same manner as in Example 1 except that a single copper layer having a thickness of 15 nm was formed by using the sputtering apparatus instead of the superlattice layer.

(Comparative Example 4)
The spin accumulator according to Comparative Example 4 was produced in the same manner as in Example 1 except that a single aluminum layer having a thickness of 15 nm was formed by using the sputtering apparatus instead of the superlattice layer.

(Comparative Example 5)
The spin accumulator according to Comparative Example 5 was produced in the same manner as in Example 1 except that a single iron layer having a thickness of 15 nm was formed by using the sputtering apparatus instead of the superlattice layer.

For each spin accumulator according to Comparative Examples 1 to 5, a spin accumulation confirmation test was conducted by the same method as for the spin accumulator according to Example 1.
The test results are summarized in Table 1 below.

As shown in Table 1, the spin evaluation voltage value of the spin accumulator according to Example 1 is an order of magnitude higher than that of each spin accumulator according to Comparative Examples 1 to 5, and the spin conduction layer is an alloy layer. It is possible to obtain remarkably excellent spin accumulation characteristics and spin supply (extraction) characteristics by forming the superlattice layer rather than forming the single layer and the single layer of the single metal layer.

(Example 2)
The stencil masks for forming electrodes having different window shapes were used, and the configuration was changed to the configuration of the spin storage device 40 shown in FIG. 6 instead of the configuration of the spin storage device 1 shown in FIG. 2 (c). The spin accumulator according to Example 2 was produced in the same manner as in Example 1.
Here, in the spin storage device according to the second embodiment, the magnetic electrode wiring is arranged so as to cross the superlattice layer four times, and the surface region of the superlattice layer is divided into five regions (FIG. 6). See regions R _{7 to} R _{11 in the} middle). The area ratio of the five regions corresponding to the regions R _{7 to} R ₁₁ in FIG. 6 is 2: 3: 5: 3: 2 (R ₇ : R ₈ : R ₉ : R) depending on the wiring spacing of the magnetic electrode wiring. ₁₀ : R ₁₁ ).

A spin accumulation confirmation test was performed on the spin storage device according to Example 2 by a method similar to the confirmation test for the spin storage device according to Example 1.
Specifically, a magnetic field of 0.5 T is applied in a direction parallel to the extending direction of each of the magnetic electrode wires as the linear portions 45a _{1 to 45a 4 shown in FIG. 6 (see B in FIG. 6).} Each of the magnetic electrodes was magnetized.
Then, a DC current of 1.0 mA was passed between the magnetic electrode wires for 5 minutes.
Next, the terminals E and F of the spin detector 10 are spun according to the second embodiment so as to straddle the _{magnetic electrode wire (corresponding to the linear portion 45a 3 in FIG. 6) at an intermediate position between the terminals E and F.} The storage device was brought into contact with the positions C and D on the surface of the superlattice layer.
Then, the voltmeter indicated a voltage with a value of 200 μV.
Further, when the energization of the 1.0 mA current flowing between the magnetic electrode wires was instantaneously stopped, the indicated value of the voltmeter became 0 V within a few seconds.
From these facts, it is confirmed that the spin accumulator according to the second embodiment has excellent spin accumulation characteristics and spin supply (extraction) characteristics as well as the spin accumulator according to the first embodiment.
Further, in contrast to the spin storage device (spin evaluation voltage: 140 μV to 150 μV) according to the first embodiment in which the magnetic electrode wire crosses the super lattice layer once, the magnetic electrode in the spin storage device according to the second embodiment. Since the wire is configured to cross the super lattice layer four times and the magnetic electrode wire as a spin supply source is densely arranged on the super lattice layer, the spin diffused and accumulated in the super lattice layer. The amount of electrons has increased, and a higher spin evaluation voltage has been obtained (spin evaluation voltage: 200 μV).

(Reference Example 2)
The area ratio of the surface region of the superlattice layer divided by the magnetic electrode wires as the _{linear portions 45a 1 to 45a 4} due to the arrangement of the electrode forming stencil mask _{(R 7} : R ₈ : R ₉ : R _10). : R ₁₁ and regions R _{7 to} R _{11 (} see FIG. 6) are all evenly changed from 2: 3: 5: 3: 2 to 3: 3: 3: 3: 3, as in Example 2. the spin accumulation device according to reference example 2 in the to prepare.
To spin accumulation device according to Reference Example 2, in an identical manner with respect to the spin accumulation device according to the second embodiment was subjected to a confirmation test spin accumulation, indication of the voltmeter using spin detector 10 The value was 1 μV or less.
From the comparison between this and the confirmation test for Example 1, the area ratio of the surface region of the two superlattice layers divided by the magnetic electrode wire (R ₇ : R ₈ : R ₉ : R ₁₀ : R ₁₁ ). Was set to 3: 3: 3: 3: 3 evenly, and approximately the same amount of upspin electrons and downspin electrons were generated in the superlattice layer with the wiring position of the magnetic electrode wire as a boundary line. It is inferred that.
That is up-spin electrons are accumulated in the regions _{R 7,} R _{9, R 11,} when a down-spin electrons are accumulated in the regions _{R 8, R 10,} in the region _{R 9,} corresponds to the linear portion _45a 2, 45a ₃ to become a spin rate of 2 times the area _{R 7, R 11} receives two spin supply from the magnetic electrode line, also, even regions _{R 8, R 10,} corresponding to the respective linear portions _45a 1 _{~45a 4} two from becoming a spin amount of 2 times the area receives a spin supply from magnetic electrode lines R _7, R ₁₁ to the accumulation amount of up-spin electrons and down-spin electrons are considered to have balanced.
Therefore, the accumulated spin electrons can be controlled depending on the surface area of the divided region, and the spin electrons of the desired polarity and the accumulated amount thereof can be controlled.

(Example 3)
The spin accumulator according to Example 3 was produced in the same manner as in Example 2 except that the constituent material of the magnetic electrode wire was changed from the permalloy alloy (in-plane magnetization) to TbFeCo (plane direct magnetization).

Except for the fact that the magnetic electrode wire was magnetized by applying a magnetic field of 0.5 T from above to the spin accumulator according to the third embodiment in a direction orthogonal to the surface of the superlattice layer (direct plane direction). When a confirmation test of spin accumulation was performed by the same method as the method for the spin accumulation device according to Example 2, the indicated value of the voltmeter using the spin detector 10 was 810 μV.
By changing the constituent material of the magnetic electrode wire to a suitable material in this way, more excellent spin accumulation characteristics and supply (extraction) characteristics can be obtained.

1,20,30,40 Spin accumulator 2,22,32,42 Substrate 3 Orientation control layer 4,24,34,44 Superlattice layer 5,25,35,35'45 Magnetic electrodes 5a, 25a, 35a, 35a _'45a 1 ~45a ₄ linear portion 5b, 25b, 35b, 35b'45b electrical connection 6 electric wiring 7 power supply 8 extraction electrode 8a wiring 8b terminal portion 10 spin detector 11 superlattice wire 12 electrode lines 51, 52 crystal alloy Layers 51a, 52a Adjacent surface

Claims (10)

With the board
The topological insulating layer arranged on the substrate and showing topological insulation and formed of an alloy material and the electrically insulating layer showing electrical insulation and formed of an alloy material different from the topological insulating layer are alternately arranged in this order. The super lattice layer that is repeatedly laminated and
A magnetic electrode arranged on the superlattice layer and having at least one linear portion straddled between two outer edges of the surface of the superlattice layer.
A spin accumulator characterized by having. The spin accumulator according to claim 1, wherein the magnetic electrode is made of a magnetic material capable of magnetizing in a direction parallel to either the in-plane direction or the perpendicular direction of the superlattice layer. 1. The spin accumulator according to the description. It has a plurality of linear portions having the same shape or a similar shape, and one said linear portion is arranged in parallel with another adjacent said linear portion and in the opposite direction to the other said linear portion. Of the three or more regions defined by the linear portion and the outer edge of the surface of the superlattice layer, the total of the regions in which spin electrons of one polarity are accumulated. The spin accumulator according to any one of claims 1 to 2, wherein the linear portion is arranged so that the surface area and the total surface area of the region where the spin electrons of other polarities are accumulated are different. The spin accumulator according to claim 4, wherein the magnetic electrode has a structure in which a linear magnetic material is folded back and bent to have a plurality of linear portions. The spin accumulator according to any one of claims 1 to 5, wherein the topological insulating layer comprises at least one of Sb, Bi, Se and Te. The spin accumulator according to any one of claims 1 to 6, wherein the electrically insulating layer contains at least one of Si, Ge, Sn, Se and Te and has a property that the spatial inversion symmetry is broken. The topological insulating layer contains at least one of Sb, Bi, Se and Te, the electrical insulating layer contains at least one of Si, Ge, Sn, Se and Te, and the spatial inversion symmetry is broken. The spin accumulator according to any one of claims 1 to 7, wherein the number of laminated superlattice layers is 10 to 50 when each layer of the topological insulating layer and the electrically insulating layer is counted as one layer. 6. Spin storage device. The spin storage device according to any one of claims 1 to 9, wherein an extraction electrode capable of extracting spin electrons accumulated in the superlattice layer is attached.

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