JP6349863B2 - Spin current thermoelectric conversion element, manufacturing method thereof, and thermoelectric conversion device - Google Patents

Description

  The present invention relates to a thermoelectric conversion element based on a spin Seebeck effect and an inverse spin Hall effect.

  In recent years, an electronic technology called “spintronics” has attracted attention. Existing electronics have used only one property of electrons, “charge”, while spintronics also actively uses other properties of electrons, “spin”. In particular, “spin-current”, which is a flow of spin angular momentum of electrons, is an important concept. Since the energy dissipation of the spin current is small, there is a possibility that highly efficient information transmission can be realized by using the spin current. Therefore, generation, detection and control of spin current are important themes.

  For example, a phenomenon is known in which a spin current is generated when a current flows. This is called the “spin-hall effect”. It is also known as an opposite phenomenon that an electromotive force is generated when a spin current flows. This is called the “inverse spin-Hall effect”. By using the inverse spin Hall effect, the generation of spin current can be detected in the form of electromotive force or current. It should be noted that both the spin Hall effect and the reverse spin Hall effect are manifested in a substance (eg, Pt, Pd) having a large “spin orbit coupling”.

Recent research has also revealed the existence of the “spin-Seebeck effect” in magnetic materials. The spin Seebeck effect is a phenomenon in which, when a temperature gradient is applied to a magnetic material, a spin current is induced in a direction parallel to the temperature gradient (see, for example, Patent Document 1 and Patent Document 2). That is, heat is converted into a spin current by the spin Seebeck effect (thermal spin current conversion). In patent document 1, the spin Seebeck effect in the NiFe film | membrane which is a ferromagnetic metal is reported. Non-Patent Documents 1 and 2 report the spin Seebeck effect at the interface between a magnetic insulator such as yttrium iron garnet (YIG, Y ₃ Fe ₅ O ₁₂ ) and an electromotive film.

  The spin current induced by the temperature gradient can be converted into an electric field (current, voltage) using the above-described inverse spin Hall effect. That is, by using the spin Seebeck effect and the inverse spin Hall effect in combination, “thermoelectric conversion” that converts a temperature gradient into electricity becomes possible.

  First, a mechanism of thermoelectric conversion of a spin-flow thermoelectric conversion element called a vertical type described in Non-Patent Document 2 will be described with reference to FIG. The vertical spin current thermoelectric conversion element is composed of a magnetic body 101 and an electromotive body 102 that are in contact with each other. When the magnetic body 101 has a magnetization 103 in the + x direction in the drawing and a temperature gradient 104 is applied in the −z direction, the thermal spin current 105 flows in the + z direction, that is, from a higher temperature to a lower temperature. The thermal spin current 105 further generates a pure spin current 106 in the electromotive body 102 through a process called spin injection between the magnetic body 101 and the electromotive body 102.

  In spin injection, a spin that precesses around the magnetization direction in the vicinity of the interface between the magnetic body 101 and the electromotive body 102 interacts with conduction electrons having no spin in the electromotive body 102, and the spin angular momentum is reduced. It is a phenomenon of passing or receiving.

  As a result, conduction electrons with spin move near the spin injection interface in the electromotive body 102 and a pure spin current is generated. In this pure spin current, conduction electrons having up spin and down spin flow in the same amount in opposite directions. As a result, there is no charge transfer, but since the signs of spins are different from each other, only the spin angular momentum flows.

  In this specification, a state where this spin injection phenomenon can occur is expressed as being magnetically coupled. This spin injection phenomenon occurs when the magnetic body 101 and the electromotive body 102 are in direct contact, or when the spin angular momentum is close enough to be transmitted even though they are not in direct contact. is there. That is, even if there is a gap between the magnetic body 101 and the electromotive body 102 or an intermediate layer is inserted, if a spin injection phenomenon can occur, it is considered that there is magnetic coupling. .

  At this time, if the electromotive body 102 is a material having a large spin-orbit interaction, a conduction electron movement 107 occurs due to the reverse spin Hall effect in a direction perpendicular to the spin current direction and the magnetization direction. A current 108 in the y direction is generated.

  In these spin current thermoelectric conversion elements, the magnitude of the electromotive force obtained is similar to the magnitude of the spin current generated in the magnetic body 101, the injection efficiency of the spin current at the interface between the magnetic body 101 and the electromotive body 102, and the electromotive force. It can be obtained by multiplying two efficiencies that are converted into electromotive force by the reverse spin Hall effect in the electric body 102. Therefore, it is necessary to simultaneously increase the three indices of the magnitude of the spin current itself, the spin current injection efficiency, and the spin current-current conversion efficiency of the electromotive body 102 in order to improve the basic performance of the spin current thermoelectric conversion element. is there.

  In addition, there are two elements that should be provided in order to efficiently use a device having a certain basic performance, that is, from a practical viewpoint. One of them is the ease of mounting on a heat source.

  Since the existing semiconductor thermoelectric conversion element has a structure in which p-type and n-type semiconductor blocks are connected in a complicated manner, it is difficult to freely change the structure of the element. Therefore, it usually has a tile shape with a flat thermal contact surface. For this reason, the heat source side must also have a flat thermal contact surface. In addition, since the thermoelectric output is improved in proportion to the size of the thermal contact surface, it is preferable to provide a thermal contact surface that is as wide and flat as possible.

  However, the portion where the waste heat is actually generated generally has a complicated surface such as a pipe through which hot water passes or a heat exchanger having a fin-type heat dissipation structure. That is, in order to mount on a surface having a complicated shape or various widths, the thermoelectric conversion element itself must be designed from the point of design for a specific heat source. As a result, it is very difficult to reduce the cost of the device.

  Another factor is the coercivity of the entire mounted device. In order for the spin Seebeck effect to appear, the magnetic material needs to be magnetized. For this purpose, it is possible to forcibly magnetize with an external magnetic field, but in practice, it is assumed that a magnetic material having a certain coercive force is used and the spin Seebeck effect is obtained by the magnetization.

  However, the magnetization of the magnetic substance may be impaired by being exposed to a high temperature state higher than the Curie temperature or being exposed to an external magnetic field higher than the coercive force. As a result, when the magnetization direction of the entire element or a part of the element is changed, the direction of the current generated in the element is also partially changed. As a result, it is expected that current cannot be efficiently generated between terminals provided in advance in the element.

  If the magnetizing process that aligns the magnetization of the magnetic material is performed again, the operation of the element is recovered, but in general, in order to magnetize, it is necessary to flow a large current through a large coil. It is practically difficult to carry out with respect to the elements mounted in the above.

JP 2009-130070 A JP 2011-249746 A Japanese Patent Laid-Open No. 7-188934 Japanese Patent Laid-Open No. 9-20980

Uchida et al. , “Spin Seeb insulator”, Nature Materials, 2010, vol. 9, p. 894. Uchida et al. “Observation of longitudinal spin-Seebeck effect in magnetic insulators”, Applied Physics Letters, 2010, vol. 97, p172505.

  As described above, in producing a practical spin current thermoelectric conversion element, it is necessary that the element size can be easily adjusted in accordance with the size of the heat source. Moreover, it must be applicable to a heat source having a non-flat heat exchange surface.

  In addition, it is necessary to use a magnetic material having excellent magnetization stability. One way to achieve this is to use the shape magnetic anisotropy of the magnetic material. Use of a magnetic material having a shape in which magnetization is difficult to reverse is effective because it can reduce the possibility of magnetization reversal and disappearance. At this time, the shape in which the magnetization is difficult to reverse is a shape that is not a sphere, and in particular, a more one-dimensional shape corresponds to it.

  However, when used as a thermoelectric conversion element, it is necessary to install the element so as to cover a certain area, and to convert a heat flow perpendicularly across the surface into electric power. That is, when the magnetic body has a one-dimensional shape, there remains a problem in the method of mounting the magnetic body in two dimensions.

  In addition, as the magnetic material becomes larger, the magnetic material may not have a single magnetization direction, but a state in which a plurality of magnetic domains having different magnetization directions coexist across the domain wall may become stable. While using the spin-flow thermoelectric conversion element, the stable state of magnetization of the magnetic material may change due to rearrangement of magnetic domains, which is a big problem in keeping the output stable.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a spin-flow thermoelectric conversion element that stabilizes output by thermoelectric conversion and has a degree of freedom of mounting on a heat source, a manufacturing method thereof, and thermoelectric conversion. Is to provide a device.

  A spin-flow thermoelectric conversion element according to the present invention includes a magnetic body and an electromotive body magnetically coupled to the magnetic body, and the magnetic body has at least one easy axis of magnetization due to shape magnetic anisotropy. And magnetizing in at least one direction of the easy magnetization axis, and the electromotive body is provided on a plane parallel to the easy magnetization axis of the magnetic body.

  The method of manufacturing a spin current thermoelectric conversion element according to the present invention is the method of manufacturing a spin current thermoelectric conversion element, wherein the magnetic body is made of a magnetic insulator fiber using a sintering method, a melting method, a crystal pulling method, or a drawing furnace. The electromotive body is formed by at least one method selected from a sputtering method, a vapor deposition method, a plating method, a screen printing method, an ink jet method, a spray method, a spin coating method, and a nanocolloid solution coating / sintering method. The magnetic material is magnetized by applying an external magnetic field.

  The thermoelectric conversion device according to the present invention includes the spin-flow thermoelectric conversion element and an output terminal that is connected to the electromotive body of the spin-flow thermoelectric conversion element and extracts a current generated by the reverse spin Hall effect of the electromotive body. .

  ADVANTAGE OF THE INVENTION According to this invention, the spin-flow thermoelectric conversion element which stabilizes the output by thermoelectric conversion, and has the freedom degree of mounting to a heat source, its manufacturing method, and a thermoelectric conversion apparatus can be provided.

It is a perspective view which shows roughly the mechanism in which a vertical spin-flow thermoelectric conversion element functions. 1 is a perspective view schematically showing a structure of a spin current thermoelectric conversion element according to a first embodiment of the present invention. It is a perspective view which shows roughly the mechanism in which the spin-flow thermoelectric conversion element which concerns on the 1st Embodiment of this invention functions. It is the figure which represented typically the module structure which concerns on the 1st Embodiment of this invention. It is the figure which represented typically the module structure of Example 1 which concerns on the 1st Embodiment of this invention. It is the figure which represented typically the thermoelectric conversion apparatus of Example 1 which concerns on the 1st Embodiment of this invention. It is the figure which represented typically the module structure of Example 2 which concerns on the 1st Embodiment of this invention. It is the figure which represented typically the structure of the spin-flow thermoelectric conversion element which concerns on the 2nd Embodiment of this invention. It is the figure which represented typically the module structure of the spin-flow thermoelectric conversion element which concerns on the 2nd Embodiment of this invention. It is the figure which represented typically the module structure of the spin-flow thermoelectric conversion element which concerns on the 2nd Embodiment of this invention. It is the figure which represented typically the structure of the thermoelectric conversion apparatus which concerns on the 3rd Embodiment of this invention.

Hereinafter, a spin-flow thermoelectric conversion element, a manufacturing method thereof, and a thermoelectric conversion device according to embodiments of the present invention will be described in detail with reference to the drawings. However, the preferred embodiments described below are technically preferable for carrying out the present invention, but the scope of the invention is not limited to the following.
(First embodiment)
(Structure of spin current thermoelectric conversion element)
First, the structure of the spin-flow thermoelectric conversion element of the first embodiment will be described with reference to FIG.

  FIG. 2 is a perspective view schematically showing the structure of the spin current thermoelectric conversion element of this embodiment. The spin current thermoelectric conversion element 201 includes a magnetic body 202 that extends in the x direction. The magnetic body 202 has a non-hollow circle, ellipse, or polygonal yz cross section, and the length in the x direction is at least twice as large as the larger length in the y or z direction. Furthermore, it is preferable to make it 10 times or more. Furthermore, an electromotive body 203 that is magnetically coupled to the magnetic body 202 is provided around the six side faces of the magnetic body 202 except for two side faces parallel to the yz plane.

The magnetic body 202 has a magnetization 204 along the x direction. If the length of the magnetic body 202 in the x direction is 100 times longer than the larger one of the y direction and the z direction, the magnetic body does not have magnetization in one direction over the whole, for example, In the case of an elongated magnetic body, it may be divided into a plurality of magnetic domains so as to divide the major axis direction, and the adjacent magnetic domains may be stabilized in a state where magnetization is reversed. In this case, in the region where the magnetization is different, the direction of the current generated by thermoelectric conversion is reversed, so that a short circuit path is generated inside the element, and the output of the element is lowered. For this reason, it is rather undesirable to make the x direction longer than necessary.
(Operation of spin-flow thermoelectric transducer)
Next, the operation of the spin current thermoelectric conversion element of this embodiment will be described with reference to FIGS.

  FIG. 3 is a perspective view schematically showing the mechanism of the function of the spin current thermoelectric conversion element of this embodiment, and schematically shows the direction of the spin current and current generated inside the spin current thermoelectric conversion element. . The spin-flow thermoelectric conversion element includes a magnetic body 301 and an electromotive body 302. The magnetic body 301 has a magnetization 303, and a case where a temperature gradient 304 is applied to the element will be described.

  The upper part of the element has the same configuration as that described with reference to FIG. 1, and an upper current 305 is generated as shown in the direction in the figure. On the other hand, the lower current 306 generated at the lower portion of the element is also generated in the same direction as the upper current 305 as a result.

  Here, the direction in which the lower current is generated will be described with reference to the xyz axis in FIG. 3, in which the xyz axis in FIG. 1 is rotated by 180 degrees about the x axis in order to confirm in detail in light of the configuration in FIG. 1. .

  Comparing FIG. 3 with FIG. 1, it can be confirmed that the directions of the magnetization 303 are the same in the + x direction. On the other hand, the temperature gradient is reversed from −z to + z, and the lower spin current 307 is generated in the direction of flowing out from the interface between the magnetic body and the electromotive body. As a result, the only difference from the configuration of FIG. 1 is that the movement of conduction electrons having up / down spins in the pure spin current generated below the electromotive body 302 is reversed. As a result, the lower current 307 is generated in the + y direction opposite to that in FIG. That is, current is generated in the same direction as the upper current 305.

  As described above, when the temperature gradient 304 is present in the entire element, current is generated in the same direction in the upper part and the lower part of the element in FIG. 3, and therefore, two opposing elements parallel to the xz plane corresponding to the side of the element in FIG. In each plane, the potential is almost equipotential in each plane, and an electromotive force is generated between the two planes. That is, by providing output terminals on two side surfaces parallel to the xz plane, current generated by the reverse spin Hall effect of the electromotive body 302 can be extracted.

  At this time, when the electromotive body 302 exists also on two surfaces parallel to the yz plane corresponding to the cross section of the element, no spin current flows in and out of this surface, and no electromotive force is generated. That is, the conductive electromotive body becomes a short-circuit path for the electromotive force generated between the xz side surfaces of the element. Therefore, it is preferable that no electromotive body exists on the two surfaces parallel to the yz plane of the element.

FIG. 4 is a schematic diagram of a spin-flow thermoelectric conversion module 402 in which two or more spin-flow thermoelectric conversion elements 401 are integrated so that their xz planes are in contact with each other. In this way, the xy plane can be covered over a wide range, and a larger heat flow 403 passes in the z-axis direction of the module. As a result, the output current 404 proportional to the area covered in the −y direction can be taken out, and the power output also increases in proportion to the area. That is, by providing output terminals on the two side surfaces at both ends parallel to the xz plane of the spin-flow thermoelectric conversion module 402, the output current 404 generated by the reverse spin Hall effect of the electromotive body can be taken out.
(Material of spin current thermoelectric conversion element)
Next, materials used for the spin-flow thermoelectric conversion element of this embodiment will be described with reference to FIG.

  The magnetic body 201 is formed of a material that exhibits a spin Seebeck effect. The magnetic material is a material having magnetism such as ferromagnetism, ferrimagnetism, and antiferromagnetism, and may be a metal, a semiconductor, or an insulator. For example, in the case of a ferromagnetic metal, a metal including at least one selected from Fe, Co, and Ni, such as NiFe, CoFe, and CoFeB, can be used.

In the case of a magnetic insulator, yttrium iron garnet (YIG, Y ₃ Fe ₅ O ₁₂ ), bismuth (Bi) doped YIG (Bi: YIG), lanthanum (La) added YIG (LaY ₂ Fe _5). O _12), yttrium gallium iron garnet _{(Y 3 Fe 5-x Ga} x O 12) can be mentioned. Further, the composition _MFe 2 _O 4 (M is a metal element, Ni, Zn, including any of Co) spinel ferrite material and the like made of.

Further, in the case of a magnetic semiconductor, the composition is selected from Fe, Co, and Ni such as CuMO ₂ and SrMO ₃ (M is a metal element and includes any of Mn, Ni, Co, and Fe), Fe ₃ O _{4, and the} like. A magnetic oxide (semiconductor oxide semiconductor) having semiconducting properties including at least one of the above. From the viewpoint of suppressing heat conduction by electrons, it is desirable to use an insulator or a semiconductor.

  As the electromotive body 202, a conductor that exhibits the reverse spin Hall effect (spin orbit interaction) can be used. For example, Au, Pt, Pd, Ni, Fe, Bi and other transition metals having a d or f orbital having a relatively large spin orbit interaction or an alloy material containing them are used. Further, the same effect can be obtained by simply doping a general metal film material such as Cu with a material such as Fe or Ir at about 0.5 to 10 mol%.

Moreover, when W, Ta, Mo, Nb, Cr, V, and Ti are used among the transition metals, a voltage having a reverse sign can be obtained from Au, Pt, Pd, or an alloy containing these. That is, the direction of the current generated by the reverse spin Hall effect is reversed. In addition, the electromotive body is an oxide conductor such as ITO (indium tin oxide) or a composition such as CuMO ₂ or SrMO ₃ (M is a metal element and includes any of Mn, Ni, Co, and Fe). It may be an oxide semiconductor.
(Method for producing spin-flow thermoelectric conversion element)
Next, the manufacturing method of the spin-flow thermoelectric conversion element of this embodiment will be described with reference to FIG.

  First, as a method for forming the magnetic body 201, a bulk body can be used as the magnetic body by using a sintering method, a melting method, a crystal pulling method, a magnetic insulator fiber forming method using a drawing furnace, or the like.

  Examples of the method for forming the electromotive body 202 include a film forming method such as a sputtering method, a vapor deposition method, a plating method, a screen printing method, an ink jet method, a spray method, and a spin coating method. Moreover, application | coating and sintering of a nano colloid solution (patent document 3, patent document 4) etc. can be used.

Hereinafter, the first embodiment will be described more specifically using examples.
Example 1
Example 1 will be described with reference to FIGS. 5 to 6 as a specific example of the present embodiment.

First, the magnetic body 502 used for the spin-flow thermoelectric conversion element 501 was produced using a sintering method. After a yttrium iron garnet (YIG, composition Y ₃ Fe ₅ O ₁₂ ) powder crushed to an average particle size of about 5 μm is heat treated in a 100% oxygen atmosphere at 800 ° C. for 24 hours, the thickness is 5 cm. Molding was performed by applying a pressure of 200 kgf / cm ^{2 to} a 3 mm circular substrate. Subsequently, a firing process was performed at 1200 ° C. for 24 hours in a 100% oxygen atmosphere, and a sintered YIG substrate serving as a base material of the magnetic body 502 was produced.

  The sintered YIG substrate was cut into a prismatic shape having a length of 3 cm and a cross section of 1 mm × 1 mm by cutting, and the entire surface was polished to obtain a magnetic body 502.

  Subsequently, the electromotive member 503 was formed using a magnetron sputtering apparatus. The magnetic body 502 after polishing is taken out into the atmosphere after HPM cleaning (hydrochloric acid hydrogen peroxide cleaning) and running water cleaning for 10 minutes, and immediately after removing moisture by blowing dry nitrogen, it is introduced into the sputter vacuum chamber. Was evacuated.

  In the sputtering vacuum chamber, the magnetic body 502 is held so that the major axis direction of the prism is parallel to the sputtering target, and the magnetic body 502 can be rotated 360 ° around the major axis direction in vacuum. It has become. As the electromotive body 503, a platinum film sputter-deposited from a 4-inch diameter platinum target was used. An electromotive body 503 was obtained by adjusting the rotational speed of the magnetic body 502, the sputtering deposition time, and the plasma output so that the thickness of the platinum film averaged to 10 nm.

  Finally, the platinum film deposited on the two end faces of 1 mm × 1 mm size was lightly polished and removed to obtain a spin current thermoelectric conversion element 501.

  A spin current thermoelectric conversion module 504 was assembled by integrating six spin current thermoelectric conversion elements 501 in the y direction and three in the z direction.

  FIG. 6 is a diagram schematically showing a thermoelectric conversion device 600 which is a mounting structure of the spin current thermoelectric conversion module 504 (601). The spin-flow thermoelectric conversion modules 601 are integrated in the spin-flow thermoelectric conversion module 601 by arranging the spin-flow thermoelectric conversion elements in an alumina mold 602 that has been prepared according to the required module size in advance. The alumina mold 602 is accurately manufactured so that the elements can be accommodated without gaps, and the two sides facing the y-axis direction are respectively plated with copper so that the inside and outside of the mold 602 are continuous. An output terminal 603 and an output terminal 604 which are applied electrodes were formed.

Through the above steps, a thermoelectric conversion device 600 that is a mounting structure of the spin current thermoelectric conversion module 601 was obtained. The internal resistance of the output terminals 603 and 604 was 2.1 ohms. The magnetic body of the module was magnetized in the x direction. When the heat bath temperature on the low temperature side was 23 ° C. in the z direction and a heat flow of 10 kW / m ² was applied from the high temperature side, the temperature difference between the high temperature side and the low temperature side was 5.5 ° C. At this time, a release voltage of 55 μV was observed between the output terminals 603 and 604.

As a result of measuring the output of the spin current thermoelectric conversion element 501 alone under the same conditions, the internal resistance was 1.0 ohm and the output voltage was 10 μV. Therefore, the effect of increasing the output power by 14.4 times can be obtained by stacking. did it. It was also confirmed that the output power can be easily increased or decreased according to the number of integrated elements.
(Modification 1 of Example 1)
Modification 1 using a commercially available platinum colloid for forming the electromotive body 503 of Example 1 will be described.

  The magnetic body 502 was produced in the same manner as in Example 1. The magnetic body 502 after the polishing treatment is O.D. D. (Optical density) Dilute to about 0.5, add 1% polyethylene glycol (average molecular weight 300 kDa), adjust the concentration and immerse in a colloidal platinum solution, and lift and dry at a rate of 1 cm / sec.

  The dried elements were each heat treated in an atmosphere of 450 ° C. for 1 hour, and then 18 elements were integrated as shown in FIG. A heat treatment at 1 ° C. for 1 hour was performed. Finally, with the elements integrated, the yz plane was lightly polished and then assembled as a thermoelectric conversion module.

In the spin current thermoelectric conversion module 601 manufactured through the above steps, the internal resistances of the output terminal 603 and the output terminal 604, which are electrodes, were 12 ohms. The magnetic body of the module was magnetized in the x direction. When the heat bath temperature on the low temperature side was 23 ° C. in the z direction and a heat flow of 10 kW / m ² was applied from the high temperature side, the temperature difference between the high temperature side and the low temperature side was 5.7 ° C. At this time, a release voltage of 28 μV was observed between the output terminal 603 and the output terminal 604.

Compared with the result of measuring the output of the spin-flow thermoelectric conversion element 501 alone under the same conditions, the effect of increasing the output power by 15.9 times was obtained by integration. It was also confirmed that the output power can be easily increased or decreased according to the number of integrated elements.
(Modification 2 of Example 1)
Modification 2 in which nickel plating is used to form the electromotive body 503 of Embodiment 1 will be described.

  The magnetic body 502 was produced in the same manner as in Example 1. The magnetic body 502 after the polishing treatment was subjected to a plating treatment so as to have a film thickness of 50 nm using a commercially available electroless nickel plating solution after washing with HPM and running water for 10 minutes.

  Furthermore, 18 elements are integrated as shown in FIG. 5, and heat treatment is performed in a vacuum at 900 ° C. for 1 hour in a state where pressure is applied in the yz direction to fix each element and spin current thermoelectric conversion. Module 504 was obtained.

The spin-flow thermoelectric conversion module 504 manufactured through the above steps had an internal resistance between output terminals of 1.3 ohms. The magnetic body of the module was magnetized in the x direction. When the heat bath temperature on the low temperature side was 23 ° C. in the z direction and a heat flow of 10 kW / m ² was applied from the high temperature side, the temperature difference between the high temperature side and the low temperature side was 5.5 ° C. At this time, a release voltage of 7.7 μV was observed between the output terminals.

Compared with the result of measuring the output of the spin-flow thermoelectric conversion element 501 alone under the same conditions, the effect of increasing the output power by 13.8 times was obtained by integration. It was also confirmed that the output power can be easily increased or decreased according to the number of integrated elements.
(Example 2)
Example 2 will be described with reference to FIG. 7 as a specific example of the present embodiment. FIG. 7 is a diagram schematically illustrating the structure of the spin-flow thermoelectric conversion module 704 according to the second embodiment.

First, a fiber-like magnetic body 702 used for the spin-flow thermoelectric conversion element 701 was produced using a drawing furnace established as a method for producing a ceramic thin wire such as an optical fiber or a sol-gel method. The fiber-like magnetic body 702 has a cylindrical side surface. Bismuth-substituted yttrium iron garnet (BYIG, composition is Bi ₁ Y ₂ Fe ₅ O ₁₂ ) was used as a raw material.

  The electromotive body 703 is provided on the cylindrical side surface of the fiber-like magnetic body 702. As the electromotive body 703, a nickel thin film manufactured using a plating method or a platinum film formed by a chemical base phase deposition method in which an organic platinum compound is baked while being sprayed can be used.

  If the magnetic body 702 is manufactured by a fiber drawing furnace or a sol-gel fiber manufacturing apparatus, and the electromotive body 703 is manufactured by a plating or firing process, most of the manufacturing process can be made a continuous process. Throughput is improved and costs can be reduced.

  Further, since a very long element connected to each other can be cut to a desired length and used, elements having various lengths can be easily created depending on the application. In addition, the portion corresponding to the cut cross section does not necessarily have an electromotive member, and therefore, it is not necessary to go through a process of removing some of the electromotive members individually. In this respect also, the throughput of device fabrication is improved and the cost is reduced.

  That is, by using this embodiment, the spin-flow thermoelectric conversion element 701 can be manufactured at a low cost, and the spin-flow thermoelectric conversion module 704 can be manufactured at a larger area and at a lower cost.

  Further, the spin current thermoelectric conversion element 701 can be easily bent and integrated. That is, even if the heat source has a cylindrical side surface like piping, a module in which the spin-flow thermoelectric conversion elements 701 are curved and integrated along the cylindrical side surface can be obtained.

  As described above, according to the spin-flow thermoelectric conversion elements according to the present embodiment and examples, the number and length of elements to be integrated and the integrated shape can be changed, so that they can be mounted on a heat source having a flat surface or a curved surface. Is possible. Furthermore, since the magnetization state of the magnetic substance is stabilized, it is possible to provide a spin current thermoelectric conversion element in which output fluctuations in thermoelectric conversion are suppressed over a long period of time.

That is, according to the present embodiment and examples, it is possible to provide a spin-flow thermoelectric conversion element that stabilizes output by thermoelectric conversion and has a degree of freedom of mounting on a heat source, a manufacturing method thereof, and a thermoelectric conversion device.
(Second Embodiment)
With reference to FIG. 8, the structure of the spin-flow thermoelectric conversion element of the 2nd Embodiment of this invention is demonstrated.

  FIG. 8 is a diagram schematically showing the structure of the spin-flow thermoelectric conversion element of this embodiment. The spin current thermoelectric conversion element 801 includes a magnetic body 802 that extends in the x direction. The magnetic body 802 has a non-hollow circle, ellipse, or polygonal yz cross section. The magnetic body 802 has a first magnetic domain 806 having a magnetization easy axis 808 in the x direction and parallel to one direction of the easy magnetization axis, and a magnetization 809 antiparallel to the magnetization 808 of the first magnetic domain 806. And having a second magnetic domain 807. The material of the magnetic body 802 can be the same as the magnetic material of the first embodiment.

  Further, the spin current thermoelectric conversion element 801 includes a first electromotive body 804 that is magnetically coupled to the first magnetic domain 806 and a second electromotive body 805 that is magnetically coupled to the second magnetic domain 807. Have. For the first and second electromotive bodies, materials in which the directions of currents generated by the reverse spin Hall effect are opposite to each other are used.

  For example, when a metal including at least one selected from Au, Pt, Pd, Ir, Ni, Fe, Co, and Bi is used for the first electromotive body 804, the second electromotive body 805 includes A metal containing at least one selected from W, Ta, Mo, Nb, Cr, V, and Ti can be used. Moreover, the material of the 1st electromotive body 804 and the 2nd electromotive body 805 may be said reverse.

  Further, the spin current thermoelectric conversion element 801 has a domain wall fixing portion 803 between the first and second magnetic domains. Thereby, the boundary of the 1st magnetic domain 806 and the 2nd magnetic domain 807 can be fixed, and the magnetization state of a magnetic body is stabilized more.

  9A and 9B show the structure of a spin-flow thermoelectric conversion module in which a plurality of spin-flow thermoelectric conversion elements 901 are integrated. In the structure of the spin current thermoelectric conversion module 900, the structure in which the first electromotive bodies 904 and the second electromotive bodies 905 are alternately connected (FIG. 9A), the first electromotive bodies 904, the second A structure in which the electromotive members 905 are connected to each other (FIG. 9B) is possible. This is because the first electromotive body 904 and the second electromotive body 905 generate electromotive forces in the same direction.

  That is, by providing output terminals on two opposing side surfaces parallel to the xz plane of the spin-flow thermoelectric conversion module 900, the current generated by the reverse spin Hall effect of the electromotive body can be taken out.

Hereinafter, the second embodiment will be described more specifically using examples.
(Example 3)
Example 3 will be described with reference to FIG. 8 as a specific example of the present embodiment.

  In the spin-flow thermoelectric conversion element 801 of this embodiment, magnetization is stabilized by intentionally introducing a domain wall that is a boundary between magnetic domains. As the magnetic body 802, a cylindrical magnetic body having a cross-section of 0.1 mmφ and a length of 10 cm is manufactured using the fiber-type element manufacturing method used in Example 2, and then a V-shaped cut is made around the column. What was processed was used.

  The V-shaped notch has a width of about 0.03 mm and a depth of 0.01 mm, and a magnetic wall 802 having a length of 10 cm is machined at one location to form a domain wall fixing portion 803. Further, with the domain wall fixing portion 803 as a boundary, the magnetic body 802 is divided into two regions, a platinum film having a thickness of 10 nm is produced as the first electromotive body 804 on one side, and the second electromotive body 805 is formed on the other side. As a result, a 7 nm thick tungsten film was produced.

  Further, the two end faces were polished to remove the metal film of the electromotive body. Finally, magnetization 808 in the region provided with the first electromotive body 804 and the region provided with the second electromotive body 805 are oriented in parallel to the long axis of the prismatic shape and in antiparallel to each other, In order to give 809, a plurality of coils corresponding to the length of each electromotive body are continuous, and magnetized using a dedicated magnetizing device that generates a magnetic field in the opposite direction.

  Through the above steps, a spin current thermoelectric conversion element 801 having a first magnetic domain 806 and a second magnetic domain 807 was obtained. Since platinum and tungsten have the property that the directions of the currents generated by the reverse spin Hall effect are opposite to each other, when the temperature gradient is the same direction, the regions equipped with the respective electromotive bodies exhibit antiparallel magnetization to each other. As a result, an electromotive force is generated in the same direction in both electromotive bodies.

  In addition, since different materials are used for the first electromotive body 804 and the second electromotive body 805, the efficiency of spin current-current conversion due to the reverse spin Hall effect is often different. In that case, it is preferable to adjust the film thickness of each electromotive body so that the magnitude of the electromotive force generated according to the internal resistance is made uniform. As a result, the generation of eddy currents accompanying local electromotive force nonuniformity can be reduced, and the element output can be maximized.

  As described above, according to the spin-flow thermoelectric conversion element according to the present embodiment and the example, the number and length of elements to be integrated and the integrated shape can be changed as in the first embodiment. It can also be mounted on a heat source with a surface. Furthermore, since the magnetization state of the magnetic substance is stabilized, it is possible to provide a spin current thermoelectric conversion element in which output fluctuations in thermoelectric conversion are suppressed over a long period of time.

That is, according to the present embodiment and examples, it is possible to provide a spin-flow thermoelectric conversion element that stabilizes output by thermoelectric conversion and has a degree of freedom of mounting on a heat source, a manufacturing method thereof, and a thermoelectric conversion device.
(Third embodiment)
With reference to FIG. 10, the structure of the spin-flow thermoelectric converter of the 3rd Embodiment of this invention is demonstrated.

  In the spin-flow thermoelectric conversion element of the present invention, the magnetic material needs to be magnetized in order to perform the thermoelectric conversion function. However, when using a magnetic material having a small coercive force, the magnetization direction may be reversed due to an external magnetic field or thermal instability. An element whose magnetization has been reversed generates an electromotive force in the opposite direction, so that the sign of the output is reversed when the element is used alone, and the output is canceled by each element when used in combination. . Therefore, it is important to suppress magnetization reversal.

  FIG. 10 is a schematic diagram of a thermoelectric conversion device 1003 including a spin current thermoelectric conversion element 1001 and a magnetization fixed element 1002 for fixing the magnetization of the magnetic material of the element. Further, the magnetization fixed element 1002 includes a permanent magnet 1004 and a conductive layer 1005. The magnetic lines of force from the permanent magnet 1004 can further stabilize the magnetization of the magnetic body 1006 of the spin-flow thermoelectric conversion element 1001.

The permanent magnet 1004 has a larger magnetization than the magnetic body of the spin current thermoelectric conversion element 1001. As a material, it is preferable to maintain stronger magnetization by combining at least one of a ferromagnetic material, a ferrimagnetic material, and an antiferromagnetic material, or a combination thereof. In addition, the thermal conductivity in the z direction is preferably equal to or less than that of the spin-flow thermoelectric conversion element 1001. For this reason, a magnetic insulator is preferable to a metal having a high thermal conductivity. For example, a bulk material such as Fe ₃ O ₄ (magnetite) can be used.

  In addition, the conductive layer 1005 needs to electrically connect the spin current thermoelectric conversion elements 1001 on both sides of the magnetization fixed element 1002. For example, the entire side surface perpendicular to the x-axis can be covered with a Cu film to form a conductive layer.

Instead of the Cu film, a metal containing at least one selected from W, Ta, Mo, Nb, Cr, V, and Ti can be used. In that case, as in the second embodiment, an output of thermoelectric conversion can be obtained also in the magnetization fixed element 1002.
As described above, according to the spin-flow thermoelectric conversion element according to the present embodiment, the number and length of elements to be integrated and the integrated shape can be changed as in the first embodiment, and thus have a flat surface or a curved surface. It can also be mounted on a heat source. Furthermore, since the magnetization state of the magnetic material of the spin-flow thermoelectric conversion element is further stabilized, it is possible to provide a spin-flow thermoelectric conversion element in which fluctuations in output in thermoelectric conversion are suppressed over a long period of time.

  That is, according to the present embodiment, it is possible to provide a spin-flow thermoelectric conversion element that stabilizes output by thermoelectric conversion and has a degree of freedom of mounting on a heat source, a manufacturing method thereof, and a thermoelectric conversion device.

  The present invention is not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

  Moreover, although a part or all of said embodiment may be described also as the following additional remarks, it is not restricted to the following.

Appendix (Appendix 1)
A magnetic body, and an electromotive body magnetically coupled to the magnetic body,
The magnetic body has at least one easy axis due to shape magnetic anisotropy, is magnetized in at least one direction of the easy axis,
The electromotive element is a spin current thermoelectric conversion element provided on a plane parallel to the easy magnetization axis of the magnetic body.
(Appendix 2)
The spin current thermoelectric conversion element according to appendix 1, wherein the magnetic body has a columnar structure having a cross section selected from a circle, an ellipse, and a polygon, and has the easy axis of magnetization in a direction perpendicular to the cross section.
(Appendix 3)
The spin current thermoelectric conversion element according to appendix 1 or 2, wherein the electromotive body is provided on a substantially entire surface substantially parallel to the easy magnetization axis of the magnetic body.
(Appendix 4)
The magnetic body has a first magnetic domain having magnetization parallel to one direction of the easy axis, and a second magnetic domain having magnetization antiparallel to the magnetization of the first magnetic domain,
The electromotive body includes a first electromotive body magnetically coupled to the first magnetic domain, and a second electromotive body magnetically coupled to the second magnetic domain,
4. The spin-flow thermoelectric conversion element according to claim 1, wherein the first and second electromotive bodies have opposite directions of currents generated by the reverse spin Hall effect.
(Appendix 5)
The spin current thermoelectric conversion element according to appendix 4, wherein the magnetic body has a domain wall fixing portion between the first and second magnetic domains.
(Appendix 6)
The magnetic body includes a metal including at least one selected from Fe, Co, and Ni,
Alternatively, yttrium iron garnet (YIG, Y3Fe5O12), YIG doped with bismuth (Bi) (Bi: YIG), lanthanum (La) added YIG (LaY2Fe5O12), yttrium gallium iron garnet (Y3Fe5-xGaxO12), MFe2O4 (M Is a metal element and includes at least one selected from spinel ferrite made of Ni, Zn, or Co),
Alternatively, the spin-flow thermoelectric conversion element according to one of appendices 1 to 5, comprising a semiconductor including at least one selected from Fe, Co, and Ni.
(Appendix 7)
The electromotive body is a metal including at least one selected from Au, Pt, Pd, Ir, Ni, Fe, Co, Bi, W, Ta, Mo, Nb, Cr, V, and Ti,
Or an oxide containing ITO (indium tin oxide),
Alternatively, the spin current thermoelectric conversion element according to one of appendices 1 to 6, comprising a semiconductor including at least one selected from Fe, Co, and Ni.
(Appendix 8)
The first electromotive body has a metal including at least one selected from Au, Pt, Pd, Ir, Ni, Fe, Co, Bi,
The spin current thermoelectric conversion element according to appendix 4 or 5, wherein the second electromotive body includes a metal including at least one selected from W, Ta, Mo, Nb, Cr, V, and Ti.
(Appendix 9)
In the method for manufacturing a spin-flow thermoelectric conversion element according to one of appendices 1 to 8,
The magnetic body is formed by at least one selected from a sintering method, a melting method, a crystal pulling method, and a magnetic insulator fiber manufacturing method using a drawing furnace,
The electromotive body is formed by at least one selected from a sputtering method, a vapor deposition method, a plating method, a screen printing method, an ink jet method, a spray method, a spin coating method, and a nanocolloid solution coating / sintering method,
A method of manufacturing a spin current thermoelectric conversion element, wherein the magnetic material is magnetized by applying an external magnetic field.
(Appendix 10)
The spin-flow thermoelectric conversion element according to any one of appendices 1 to 8,
A thermoelectric conversion device comprising: an output terminal connected to an electromotive body of the spin-flow thermoelectric conversion element and taking out a current generated by a reverse spin Hall effect of the electromotive body.
(Appendix 11)
The thermoelectric conversion device according to appendix 10, wherein a plurality of the spin current thermoelectric conversion elements are integrated.
(Appendix 12)
The thermoelectric conversion device according to appendix 10 or 11, further comprising a magnetization fixed element having a permanent magnet, wherein magnetic lines of force from the permanent magnet reach the magnetic body of the spin current thermoelectric conversion element.
(Appendix 13)
The thermoelectric conversion device according to appendix 12, wherein the magnetization of the permanent magnet is larger than the magnetization of the magnetic body of the spin current thermoelectric conversion element.

101, 202, 301, 502, 802, 1006 Magnetic body 102, 203, 302, 503, 703 Electromotive body 103, 204, 303, 808, 809 Magnetization 104, 304 Temperature gradient 105 Thermal spin current 106 Pure spin current 107 Reverse Movement of conduction electrons by spin Hall effect 108 Current 201, 401, 501, 701, 801, 901, 1001 Spin current thermoelectric conversion element 305 Upper current 306 Lower current 307 Lower spin current 402, 504, 601, 704, 900 Spin current thermoelectric Conversion module 403 Heat flow 404 Output current 600, 1003 Thermoelectric conversion device 602 Form 603, 604 Output terminal 702 Fiber-like magnetic body 803 Domain wall fixing part 804, 904 First electromotive body 805, 905 Second electromotive body 806 First 1 magnetic domain 807 Magnetic domain 1002 magnetization fixed element 1004 permanent magnet 1005 conductive layer

Claims (10)

A magnetic body, and an electromotive body magnetically coupled to the magnetic body,
The magnetic body has at least one easy axis due to shape magnetic anisotropy, is magnetized in at least one direction of the easy axis,
The electromotive element is a spin current thermoelectric conversion element provided on all surfaces substantially parallel to the easy magnetization axis of the magnetic body.   The spin current thermoelectric conversion element according to claim 1, wherein the magnetic body has a columnar structure having a cross section selected from a circle, an ellipse, and a polygon, and has the easy axis of magnetization in a direction perpendicular to the cross section.   The magnetic body has a first magnetic domain having magnetization parallel to one direction of the easy axis, and a second magnetic domain having magnetization antiparallel to the magnetization of the first magnetic domain,
  The electromotive body includes a first electromotive body magnetically coupled to the first magnetic domain, and a second electromotive body magnetically coupled to the second magnetic domain,
  3. The spin current thermoelectric conversion element according to claim 1, wherein the first and second electromotive bodies have opposite directions of currents generated by an inverse spin Hall effect.   The magnetic body includes a metal including at least one selected from Fe, Co, and Ni,
  Or yttrium iron garnet (YIG, Y ₃ Fe ₅ O ₁₂ ), YIG doped with bismuth (Bi) (Bi: YIG), YIG with added lanthanum (La) (LaY) ₂ Fe ₅ O ₁₂ ), Yttrium gallium iron garnet (Y ₃ Fe _5-x Ga _x O ₁₂ ), MFe ₂ O ₄ An insulator including at least one selected from spinel ferrites (M is a metal element and includes any one of Ni, Zn, and Co);
  The spin-flow thermoelectric conversion element according to claim 1, further comprising a semiconductor containing at least one selected from Fe, Co, and Ni.   The electromotive body is a metal including at least one selected from Au, Pt, Pd, Ir, Ni, Fe, Co, Bi, W, Ta, Mo, Nb, Cr, V, and Ti,
  Or an oxide containing ITO (indium tin oxide),
  5. The spin-flow thermoelectric conversion element according to claim 1, further comprising a semiconductor including at least one selected from Fe, Co, and Ni.   A magnetic body, and an electromotive body magnetically coupled to the magnetic body,
  The magnetic body has at least one easy axis due to shape magnetic anisotropy, is magnetized in at least one direction of the easy axis,
  A first magnetic domain having a magnetization parallel to one direction of the easy axis, and a second magnetic domain having a magnetization antiparallel to the magnetization of the first magnetic domain;
  The electromotive body is provided on a plane parallel to the easy magnetization axis of the magnetic body,
  A first electromotive body magnetically coupled to the first magnetic domain; and a second electromotive body magnetically coupled to the second magnetic domain;
  The first and second electromotive elements are spin current thermoelectric conversion elements in which directions of currents generated by an inverse spin Hall effect are opposite to each other.   In the manufacturing method of the spin-flow thermoelectric conversion element according to claim 1,
  The magnetic body is formed by at least one selected from a sintering method, a melting method, a crystal pulling method, and a magnetic insulator fiber manufacturing method using a drawing furnace,
  The electromotive body is formed by at least one selected from a sputtering method, a vapor deposition method, a plating method, a screen printing method, an ink jet method, a spray method, a spin coating method, and a nanocolloid solution coating / sintering method,
  A method of manufacturing a spin current thermoelectric conversion element, wherein the magnetic material is magnetized by applying an external magnetic field.   The spin-flow thermoelectric conversion element according to claim 1,
  A thermoelectric conversion device comprising: an output terminal connected to an electromotive body of the spin-flow thermoelectric conversion element and taking out a current generated by a reverse spin Hall effect of the electromotive body.   The thermoelectric conversion device according to claim 8, further comprising a magnetization fixed element having a permanent magnet, wherein magnetic lines of force from the permanent magnet reach the magnetic body of the spin current thermoelectric conversion element.   The thermoelectric conversion device according to claim 9, wherein the magnetization of the permanent magnet is larger than the magnetization of the magnetic body of the spin-flow thermoelectric conversion element.