JPWO2013153949A1 - Magnetic field measuring apparatus and magnetic field measuring method - Google Patents

Abstract

The magnetic field measurement apparatus includes a magnetic layer, an electromotive layer, and a magnetic field information generation unit. The electromotive layer is formed on the magnetic layer and is made of a material that exhibits spin-orbit interaction. The magnetic field information generation unit generates magnetic field information related to the magnetic field applied to the magnetic layer based on information related to the electromotive force generated in the electromotive layer.

Description

  The present invention relates to a magnetic field measuring apparatus and a magnetic field measuring method.

  In recent years, an electronic technology called “spintronics” has been spotlighted. Conventional electronics have used only “charge”, which is one property of electrons, while spintronics also actively uses “spin”, which is another property of electrons. In particular, the “spin-current”, which is the flow of electron spin angular momentum, is an important concept. Since the energy dissipation of the spin current is small, there is a possibility that highly efficient information transfer 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 the “spin-Hall effect (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 spin current can be detected. It should be noted that both the spin Hall effect and the reverse spin Hall effect are significantly expressed in a substance (eg, Pt, Au) having a large “spin orbit coupling”.

Recent studies have 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, Non-Patent Document 1, and Non-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 a metal 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.

  FIG. 1 shows a configuration of a thermoelectric conversion element disclosed in Patent Document 1. A thermal spin current conversion unit 102 is formed on the sapphire substrate 101. The thermal spin current conversion unit 102 has a stacked structure of a Ta film 103, a PdPtMn film 104, and a NiFe film 105. The NiFe film 105 has in-plane magnetization. Further, a Pt electrode 106 is formed on the NiFe film 105, and both ends of the Pt electrode 106 are connected to terminals 107-1 and 107-2, respectively.

  In the thermoelectric conversion element configured as described above, the NiFe film 105 plays a role of generating a spin current from the temperature gradient by the spin Seebeck effect, and the Pt electrode 106 generates an electromotive force from the spin current by the reverse spin Hall effect. Play a role. Specifically, when a temperature gradient is applied in the in-plane direction of the NiFe film 105, a spin current is generated in a direction parallel to the temperature gradient due to the spin Seebeck effect. Then, a spin current flows from the NiFe film 105 to the Pt electrode 106 or a spin current flows from the Pt electrode 106 to the NiFe film 105. In the Pt electrode 106, an electromotive force is generated in a direction orthogonal to the spin current direction and the NiFe magnetization direction by the inverse spin Hall effect. The electromotive force can be taken out from terminals 107-1 and 107-2 provided at both ends of the Pt electrode 106.

  On the other hand, in order to realize a safe and secure society, technologies for sensing various physical quantities in various situations are expected. In particular, magnetic sensors that detect magnetic fields (magnetic fields) are accelerating their application in various application fields such as door / panel opening / closing detection, motor control, and vehicle pedal position detection. Conventional magnetic sensors are roughly classified into two types: a magnetoresistive (MR) type sensor (for example, Patent Document 2) and a Hall element type sensor (for example, Patent Document 3).

JP 2009-130070 A JP 2005-049262 A JP 2001-337147 A

Uchida et al., “Spin Seebeck 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.

  The magnetic sensors described in Patent Document 2 and Patent Document 3 detect a magnetic field through changes in magnetic resistance and Hall resistance. In order to detect such a change in magnetic resistance or Hall resistance, it is necessary to apply a bias voltage across the element using an external power source. Therefore, power consumption during magnetic field measurement is increased.

  An object of the present invention is to provide a magnetic field measuring apparatus and a magnetic field measuring method capable of reducing power consumption during magnetic field measurement.

  In one aspect of the present invention, a magnetic field measurement apparatus is provided. The magnetic field measurement apparatus includes a magnetic layer, an electromotive layer, and a magnetic field information generation unit. The electromotive layer is formed on the magnetic layer and is made of a material that exhibits spin-orbit interaction. The magnetic field information generation unit generates magnetic field information related to the magnetic field applied to the magnetic layer based on information related to the electromotive force generated in the electromotive layer.

  In another aspect of the present invention, a magnetic field measurement method is provided. The magnetic field measurement method includes the step of (A) providing a thermoelectric conversion element. The thermoelectric conversion element includes a magnetic layer and an electromotive layer formed on the magnetic layer and formed of a material that exhibits spin-orbit interaction. The magnetic field measurement method further includes (B) generating magnetic field information related to the magnetic field applied to the magnetic layer based on information related to the electromotive force generated in the electromotive layer.

  According to the magnetic field measurement apparatus and the magnetic field measurement method of the present invention, it is possible to reduce power consumption during magnetic field measurement.

FIG. 1 is a schematic diagram showing a thermoelectric conversion element described in Patent Document 1. As shown in FIG. FIG. 2 schematically shows the configuration of the magnetic field measuring apparatus according to the first embodiment of the present invention. FIG. 3A is a schematic diagram for explaining the operation of the magnetic field measuring apparatus shown in FIG. FIG. 3B is a schematic diagram for explaining the operation of the magnetic field measuring apparatus shown in FIG. FIG. 4 is a graph showing the characteristics of the magnetic field measuring apparatus according to the embodiment of the present invention. FIG. 5 schematically shows the configuration of a magnetic field measuring apparatus according to the second embodiment of the present invention. FIG. 6 schematically shows a configuration of a magnetic field measuring apparatus according to the third embodiment of the present invention. FIG. 7 schematically shows a configuration of a magnetic field measuring apparatus according to the fourth embodiment of the present invention. FIG. 8 shows an example of a plane pattern of the electromotive layer in the fourth embodiment of the present invention. FIG. 9A shows an electromotive state in the electromotive layer shown in FIG. FIG. 9B shows an electromotive state in the electromotive layer shown in FIG. FIG. 10 shows another example of the plane pattern of the electromotive layer in the fourth exemplary embodiment of the present invention. FIG. 11A shows an electromotive state in the electromotive layer shown in FIG. FIG. 11B shows an electromotive state in the electromotive layer shown in FIG. FIG. 12 shows still another example of the plane pattern of the electromotive layer in the fourth exemplary embodiment of the present invention. FIG. 13 shows still another example of the plane pattern of the electromotive layer in the fourth embodiment of the present invention. FIG. 14 shows still another example of the plane pattern of the electromotive layer in the fourth embodiment of the present invention. FIG. 15 schematically shows an example of the configuration of a magnetic field measuring apparatus according to the fifth embodiment of the present invention. FIG. 16 schematically shows another example of the configuration of the magnetic field measurement apparatus according to the fifth embodiment of the present invention. FIG. 17A is a schematic diagram for explaining an application example of the magnetic field measurement apparatus according to the embodiment of the present invention. FIG. 17B is a schematic diagram for explaining an application example of the magnetic field measurement apparatus according to the embodiment of the present invention. FIG. 18A is a graph for explaining the operation of the magnetic field measurement apparatus according to the embodiment of the present invention. FIG. 18B is a graph for explaining the operation of the magnetic field measurement apparatus according to the embodiment of the present invention. FIG. 19 is a graph for explaining the operation of the magnetic field measurement apparatus according to the embodiment of the present invention.

  A magnetic field measuring apparatus and a magnetic field measuring method according to embodiments of the present invention will be described with reference to the accompanying drawings.

1. First Embodiment FIG. 2 schematically shows a configuration of a magnetic field measurement apparatus 1 according to a first embodiment of the present invention. The magnetic field measurement apparatus 1 includes a magnetic layer 20, an electromotive layer 30, and a magnetic field information generation unit 40. The electromotive layer 30 is formed on the magnetic layer 20. That is, the magnetic layer 20 and the electromotive layer 30 are laminated. This stacking direction is hereinafter referred to as the Z direction. In-plane directions orthogonal to the Z direction are the X direction and the Y direction. The X direction and the Y direction are orthogonal to each other.

The magnetic layer 20 is a heat-spin current converter that exhibits a spin Seebeck effect. That is, the magnetic layer 20 generates (drives) the spin current j _s from the temperature gradient ∇T by the spin Seebeck effect. The direction of the spin current j _s is parallel or antiparallel to the direction of the temperature gradient ∇T. In the example shown in FIG. 2, a temperature gradient ∇T in the + Z direction is applied, and a spin current j _s along the + Z direction or the −Z direction is generated. As will be described later, the magnetic layer 20 preferably contains a soft magnetic material as a main component.

The electromotive layer 30 is a spin current-current converter that exhibits a reverse spin Hall effect (spin orbit interaction). That is, the electromotive layer 30 generates an electromotive force from the spin current j _s by the inverse spin Hall effect. The electromotive layer 30 contains a material having a large “spin orbit interaction”. For example, Au, Pt, Pd, Ir, other metal materials having f orbitals having a relatively large spin-orbit interaction, or alloy materials containing them are used. The same effect can be obtained by simply doping a general metal film material such as Cu with a material such as Au, Pt, Pd, or Ir by about 0.5 to 10%. The electromotive layer 30 may be an oxide such as ITO. From the viewpoint of measurement sensitivity, the thickness of the electromotive layer 30 is preferably set to about the spin diffusion length of the metal material or less in order to effectively use the spin current signal. For example, it is desirable to set to 50 nm for Au and to about 10 nm for Pt.

  The lamination of the magnetic layer 20 and the electromotive layer 30 constitutes a thermoelectric conversion element (spin Seebeck thermoelectric element). Hereinafter, the electromotive force generated by such a thermoelectric conversion element will be described with reference to FIGS. 3A and 3B.

FIG. 3A shows a situation in which the external magnetic field H in the −Y direction is uniformly applied to the entire element. When the magnetic layer 20 is formed of a soft magnetic material, the direction of the magnetization M is the same as the −Y direction as the external magnetic field H. In addition, when a temperature gradient ∇T in the + Z direction is applied to the magnetic layer 20, the spin current j _s flows into the electromotive layer 30. In the electromotive layer 30, as a result of the reverse spin Hall effect, an electromotive field E _ISHE represented by the following formula (1) is generated.

In the above formula (1), θ _H represents the spin Hall angle, ρ represents the resistivity of the electromotive layer 30, and j _s represents the interface spin current driven by the spin Seebeck effect.

Here, the amount of the driven spin current j _s depends not only on the temperature gradient ∇T but also on the magnitude of the magnetization M. Since the magnitude of the magnetization M depends on the external magnetic field H, the spin current j _s is expressed as a function j _s (∇T, H) of the applied temperature gradient ∇T and the external magnetic field H. The direction of the spin current j _s is the −Z direction opposite to the temperature gradient ∇T (+ Z direction) in the example of FIG. 3A.

In addition, the electromotive field E _ISHE depends on the outer product of the spin current j _s and the magnetization M (that is, the external magnetic field H). Therefore, the electromotive field E _{ISHE is} also expressed as a function E _ISHE (∇T, H) of the applied temperature gradient ∇T and the external magnetic field H. The magnitude of the electromotive field E _ISHE depends on the magnitude of the temperature gradient ∇T and the magnitude of the external magnetic field H. The direction of the electromotive force E _ISHE is given by the direction of the outer product (H × ∇T) of the external magnetic field H and the temperature gradient ∇T, and is the + X direction in the example of FIG. 3A.

  Here, two points separated in the X direction on the electromotive layer 30 are considered. The electromotive force V (output voltage) observed between the two points is given by the following line integral equation (2) with the integration range between the two points.

The electromotive force V generated in the electromotive layer 30 is also expressed as a function V (∇T, H) of the applied temperature gradient ∇T and the external magnetic field H. In the example shown in FIG. 3A, the electromotive field E _ISHE is constant over the electromotive layer 30, and the direction of the electromotive force V is the + X direction.

  FIG. 3B shows a situation in which the direction of the external magnetic field H applied to the element is the opposite direction to that in FIG. 3A, that is, the + Y direction. In this case, the direction of the magnetization M of the magnetic layer 20 made of a soft magnetic material is the same as the + Y direction as the external magnetic field H. If the other conditions are the same as those in FIG. 3A, only the direction of the electromotive force V changes and becomes the −X direction.

  Thus, the direction of the electromotive force V generated in the electromotive layer 30 changes according to the direction of the external magnetic field H applied to the element. Therefore, by observing the direction of the electromotive force V, at least the direction of the external magnetic field H can be detected.

  FIG. 4 shows the relationship between the external magnetic field H and the electromotive force V in more detail. Here, only the magnetic field component Hy in the Y direction as shown in FIGS. 3A and 3B is considered.

  As the magnetic field component Hy in the -Y direction increases from 0, the absolute value of the electromotive force V increases accordingly. When the magnetic field component Hy in the −Y direction exceeds a certain value “−Hsy”, the electromotive force V is saturated at a certain constant value “−Vs”. This region (Hy <−Hsy) where the electromotive force V is a constant value “−Vs” is hereinafter referred to as “saturation region RSA”.

  Similarly, as the magnetic field component Hy in the + Y direction increases from 0, the absolute value of the electromotive force V increases accordingly. When the magnetic field component Hy in the + Y direction exceeds a certain value “Hsy”, the electromotive force V is saturated at a certain constant value “Vs”. This region (Hy> Hsy) where the electromotive force V is a constant value “Vs” is hereinafter referred to as “saturation region RSB”.

  A region between the saturation region RSA and the saturation region RSB (−Hsy <Hy <Hsy) is hereinafter referred to as “transient region RT”. In the transient region RT, the magnitude of the electromotive force V varies according to the variation in the magnitude of the magnetic field component Hy.

In the case of the saturation regions RSA and RSB, information on the direction of the magnetic field component Hy can be obtained from the information on the electromotive force V. Regarding the magnitude of the magnetic field component Hy, information “Hy <−Hsy” or “Hy> Hsy” is obtained. Can only be obtained. That is, the absolute value of the magnetic field component Hy cannot be detected. On the other hand, in the case of the transient region RT, both the direction and absolute value of the magnetic field component Hy can be detected from the information on the electromotive force V. For example, when the magnitude of the electromotive force V is “V ₁ ”, it can be seen from the graph of FIG. 4 that the magnitude of the magnetic field component Hy is “H ₁ ”.

  A circuit for estimating the external magnetic field H from the electromotive force V by such a method is the “magnetic field information generation unit 40”. As shown in FIGS. 2, 3 </ b> A, and 3 </ b> B, the magnetic field information generation unit 40 is connected to the electromotive layer 30. Then, the magnetic field information generation unit 40 generates information (direction, magnitude) related to the external magnetic field H based on information (direction, magnitude) related to the electromotive force V generated in the electromotive layer 30. At this time, the magnetic field information generation unit 40 refers to the voltage-magnetic field characteristics as shown in FIG. Such voltage-magnetic field characteristics may be tabulated or mathematically expressed and mounted on the magnetic field information generation unit 40. Information regarding the external magnetic field H generated by the magnetic field information generation unit 40 is hereinafter referred to as “magnetic field information DH”. The magnetic field information generation unit 40 outputs the generated magnetic field information DH.

  When it is desired to acquire the magnetic field information DH regarding the absolute value of the external magnetic field H, the operation in the transient region RT is desirable as described above. Therefore, a magnetic material having a saturation magnetic field (−Hsy, Hsy) that makes the transient region RT wider than the measurement target range of the external magnetic field H is preferably used as the material of the magnetic layer 20.

  In order to detect the direction with high sensitivity even when the magnitude of the external magnetic field H is small, it is preferable to use a soft magnetic material having a small coercive force as the material of the magnetic layer 20. Specifically, it is desirable to use a soft magnetic material having a coercive force of 10 Oe or less, and a coercive force of 1 Oe or less is more desirable when performing highly sensitive magnetic field measurement.

  In order to increase the thermoelectric conversion efficiency, it is conceivable to increase the temperature difference between the front and back surfaces of the magnetic layer 20 by using a low thermal conductivity material for the magnetic layer 20. It is also effective to suppress the current generated in the electromotive layer 30 from flowing into the magnetic layer 20 by using a magnetic insulating material having a low electrical conductivity for the magnetic layer 20.

  Considering these, it is conceivable to use a soft ferrite material such as yttrium iron garnet (YIG) or Mn—Zn ferrite as the material of the magnetic layer 20. Note that the magnetic layer 20 does not need to be formed entirely of a soft magnetic material, and may contain a soft magnetic material as a main component.

(effect)
As described above, according to the present embodiment, a novel magnetic field measurement apparatus 1 using a thermoelectric conversion element (spin Seebeck thermoelectric element) is provided. According to the magnetic field measurement apparatus 1 according to the present embodiment, an electromotive force V corresponding to the external magnetic field H is generated if the temperature gradient ∇T exists. Therefore, information on the external magnetic field H can be obtained based on information on the generated electromotive force V.

  According to the techniques described in Patent Document 2 and Patent Document 3 described above, magnetic field measurement is performed through changes in magnetic resistance and Hall resistance. In order to detect such a change in magnetic resistance or Hall resistance, it is necessary to apply a bias voltage across the element using an external power source. This leads to an increase in power consumption and standby power during magnetic field measurement, and causes wiring and circuit complexity.

  On the other hand, according to the present embodiment, it is not necessary to apply a bias voltage to both ends of the element using an external power source during magnetic field measurement. Therefore, power consumption and standby power during magnetic field measurement are reduced. In addition, wiring and circuits can be simplified.

  It can be said that the magnetic field measurement apparatus 1 according to the present embodiment uses familiar heat as an energy source instead of an external power source. In addition, an electronic device etc. can be considered as such a heat source.

2. Second Embodiment FIG. 5 schematically shows a configuration of a magnetic field measuring apparatus 1 according to a second embodiment of the present invention. The magnetic layer 20 is formed on the substrate 10. The first terminal 51 and the second terminal 52 are formed at different positions on the electromotive layer 30. The magnetic field information generation unit 40 is connected to the first terminal 51 via the first wiring 61 and is connected to the second terminal 52 via the second wiring 62. Then, the magnetic field information generation unit 40 generates magnetic field information DH based on information about the electromotive force V between the first terminal 51 and the second terminal 52.

  In the example shown in FIG. 5, the first terminal 51 and the second terminal 52 are provided on the electromotive layer 30 at positions separated in the X direction. Therefore, the magnetic field information generation unit 40 generates magnetic field information DH related to the magnetic field component in the Y direction of the external magnetic field H based on the information related to the electromotive force V in the X direction between the first terminal 51 and the second terminal 52. be able to.

  In the example shown in FIG. 5, each of the first terminal 51 and the second terminal 52 is formed long in one direction, and the longitudinal direction thereof is the Y direction orthogonal to the X direction. With such a structure, it is possible to reliably detect the X component of the electromotive force between the first terminal 51 and the second terminal 52 and accurately measure the Y-direction magnetic field component.

  Further, the surface resistance of each of the first terminal 51 and the second terminal 52 is preferably lower than the surface resistance of the electromotive layer 30. For example, each of the first terminal 51 and the second terminal 52 is formed of a metal material such as Cu, Au, or Al having a thickness of 100 nm or more.

  Various means for applying a temperature gradient ∇T to the element are conceivable. For example, a heat source is disposed close to one side or both sides of the element. Alternatively, the substrate 10 itself may be a heat source.

3. Third Embodiment In the third embodiment of the present invention, in order to generate magnetic field information DH for each of magnetic field components in different directions, a different magnetic field information generation unit 40 is provided for each magnetic field component. For example, FIG. 6 shows a magnetic field measuring apparatus 1 that can detect both X-direction and Y-direction magnetic field components with respect to the external magnetic field H.

  An X-direction magnetic field information generation unit 40X is provided as the magnetic field information generation unit 40 for the X-direction magnetic field component. The X-direction magnetic field information generation unit 40X generates X-direction magnetic field information DH-X related to the X-direction magnetic field component based on information related to the Y-direction electromotive force V generated in the electromotive layer 30. More specifically, the first terminal 51X and the second terminal 52X are formed on the electromotive layer 30 at positions separated in the Y direction. The X-direction magnetic field information generation unit 40X is connected to the first terminal 51X via the first wiring 61X, and is connected to the second terminal 52X via the second wiring 62X. Then, the X-direction magnetic field information generation unit 40X generates the X-direction magnetic field information DH-X based on information on the electromotive force V in the Y direction between the first terminal 51X and the second terminal 52X.

  On the other hand, a Y-direction magnetic field information generation unit 40Y is provided as the magnetic field information generation unit 40 for the Y-direction magnetic field component. The Y-direction magnetic field information generation unit 40Y generates Y-direction magnetic field information DH-Y related to the Y-direction magnetic field component based on the information related to the X-direction electromotive force V generated in the electromotive layer 30. More specifically, the first terminal 51Y and the second terminal 52Y are formed on the electromotive layer 30 at positions separated in the X direction. The Y-direction magnetic field information generation unit 40Y is connected to the first terminal 51Y via the first wiring 61Y, and is connected to the second terminal 52Y via the second wiring 62Y. And the Y direction magnetic field information generation part 40Y produces | generates Y direction magnetic field information DH-Y based on the information regarding the electromotive force V of the X direction between the 1st terminal 51Y and the 2nd terminal 52Y.

  In order to equalize the sensitivity to the X direction magnetic field component and the Y direction magnetic field component, the shape and arrangement of the terminal pair (51X, 52X) in the X direction and the shape and arrangement of the terminal pair (51Y, 52Y) in the Y direction Should be equivalent.

4). Fourth Embodiment As can be seen from the above equation (2), the electromotive force V also depends on the length of the electromotive layer 30 between the first terminal 51 and the second terminal 52. If the electromotive field E _ISHE is constant, the electromotive force V increases in proportion to the length of the electromotive layer 30 between the first terminal 51 and the second terminal 52. This means that even if the external magnetic field H changes by the same amount, the electromotive force V changes more greatly. That is, measurement sensitivity can be increased by increasing the length of the electromotive layer 30 between the first terminal 51 and the second terminal 52.

  However, in the case of the rectangular electromotive layer 30 as shown in FIG. 5 and the like, it is not preferable to simply lengthen the electromotive layer 30 in one direction because it increases the element area. Thus, in the fourth embodiment of the present invention, the electromotive layer 30 between the first terminal 51 and the second terminal 52 is devised in the formation pattern of the electromotive layer 30 on the magnetic layer 20. Consider increasing the “effective length”.

  For example, as shown in FIG. 7, a pattern in which a long and thin electromotive layer 30 is bent a plurality of times can be considered. And the 1st terminal 51 and the 2nd terminal 52 are each formed in the both ends of the electromotive layer 30 of such a pattern. In this case, the length (that is, the effective length) along the extending direction of the electromotive layer 30 between the first terminal 51 and the second terminal 52 is larger than the length of one side of the magnetic layer 20. Much longer. That is, the effective length of the electromotive layer 30 can be increased without increasing the element area.

  FIG. 8 shows an example of the plane pattern of the electromotive layer 30 in this embodiment in detail. A pattern in which a plurality of elongated electromotive layers 30 are bent is formed, and a first terminal 51 and a second terminal 52 are provided at both ends thereof. Here, the extending direction of each part of the electromotive layer 30 when the electromotive layer 30 is traced from the first terminal 51 toward the second terminal 52 will be considered. In this case, the electromotive layer 30 includes an electromotive portion 30A having an extending direction A direction, an electromotive portion 30B having an extending direction B direction, an electromotive portion 30C having an extending direction C direction, and an extending portion. The current direction is divided into electromotive portions 30D having a D direction. Here, the A direction and the B direction are orthogonal, the B direction and the C direction are orthogonal, the C direction and the D direction are orthogonal, the D direction and the A direction are orthogonal, and the A direction and The C direction is antiparallel, and the B direction and D direction are antiparallel. Then, from the first terminal 51 toward the second terminal 52, the electromotive portion repeatedly appears in the order of “30A, 30B, 30C, 30D, 30A. As a result, a “spiral” planar pattern as shown in FIG. 8 is formed.

  Next, with reference to FIG. 9A and FIG. 9B, the electromotive state when the external magnetic field H is applied regarding the electromotive layer 30 shown in FIG. 8 will be considered. Here, as an example, a case where the electromotive layer 30 is uniformly formed of a single material is considered. Further, it is assumed that the widths of the electromotive portions 30A, 30B, 30C, and 30D are substantially the same, and the overall lengths thereof are also substantially the same.

FIG. 9A shows a case where an external magnetic field H in the + X direction is applied. In this case, at each point of the electromotive layer 30, an electromotive field E _ISHE in the + Y direction is generated. Therefore, in the electromotive portions 30A and 30B, there is an electromotive field E _{ISHE in the} direction opposite to the extending directions A and B, that is, in the direction from the second terminal 52 to the first terminal 51 along the electromotive layer 30. Occur. On the other hand, in the electromotive portions 30C and 30D, an electromotive field E _ISHE is generated in the same direction as the extending directions C and D, that is, in the direction from the first terminal 51 to the second terminal 52 along the electromotive layer 30. To do.

  The total amount of electromotive force V traveling from the first terminal 51 to the second terminal 52 along the electromotive layer 30 is hereinafter referred to as “first electromotive force V1”. On the other hand, the total amount of electromotive force V from the second terminal 52 toward the first terminal 51 along the electromotive layer 30 is hereinafter referred to as “second electromotive force V2”. In the example shown in FIG. 9A, the electromotive parts 30C and 30D contribute to the first electromotive force V1, and the electromotive parts 30A and 30B contribute to the second electromotive force V2. And the 1st electromotive force V1 and the 2nd electromotive force V2 become substantially equal. That is, the first electromotive force V1 and the second electromotive force V2 cancel each other, and the electromotive force V (output voltage) between the first terminal 51 and the second terminal 52 becomes almost zero.

FIG. 9B shows a case where an external magnetic field H in the + Y direction is applied. In this case, an electromotive field E _ISHE in the −X direction is generated at each point of the electromotive layer 30. Therefore, in the electromotive portions 30B and 30C, there is an electromotive field E _{ISHE in the} direction opposite to the extending directions B and C, that is, in the direction from the second terminal 52 to the first terminal 51 along the electromotive layer 30. Occur. On the other hand, in the electromotive portions 30D and 30A, an electromotive field E _ISHE is generated in the same direction as the extending directions D and A, that is, in the direction from the first terminal 51 to the second terminal 52 along the electromotive layer 30. To do. Accordingly, as in the case of FIG. 9A, the first electromotive force V1 and the second electromotive force V2 cancel each other, and the electromotive force V (output voltage) between the first terminal 51 and the second terminal 52 becomes substantially zero. turn into.

  As described above, when the electromotive layer 30 having a planar pattern as shown in FIG. 8 is uniformly formed of a single material, the first electromotive force V1 and the second electromotive force V2 cancel each other, and the thermoelectric conversion is performed. Efficiency is very poor. That is, the advantage obtained by increasing the “effective length” of the electromotive layer 30 between the first terminal 51 and the second terminal 52 cannot be sufficiently obtained.

  Therefore, it is preferable to form the electromotive layer 30 so that the first electromotive force V1 and the second electromotive force V2 are as asymmetric as possible. For this purpose, the electromotive conversion efficiency (spin Hall effect) may be different between the electromotive portion contributing to the first electromotive force V1 and the electromotive portion contributing to the second electromotive force V2.

  For example, an electromotive layer 30 as shown in FIG. 10 can be considered. The plane pattern of the electromotive layer 30 shown in FIG. 10 is the same as that shown in FIG. However, the material of the electromotive layer 30 is not uniform, and materials having different thermoelectric conversion efficiencies are mixed. Specifically, the spin-orbit interaction (spin Hall effect) of the material of the electromotive parts 30A and 30B is smaller than that of the material of the electromotive parts 30C and 30D. Therefore, the thermoelectric conversion efficiency in the electromotive portions 30A and 30B is lower (suppressed) than that in the electromotive portions 30C and 30D. The electromotive state in the electromotive layer 30 when the external magnetic field H is applied is as follows.

  FIG. 11A shows a case where an external magnetic field H in the + X direction is applied. At this time, the first electromotive force V1 in the direction from the first terminal 51 to the second terminal 52 is generated by the electromotive portions 30C and 30D as in the case of FIG. 9A described above. On the other hand, since the spin Hall effect of the electromotive portions 30A and 30B contributing to the second electromotive force V2 is small, the second electromotive force V2 becomes very small. That is, the first electromotive force V1 and the second electromotive force V2 are asymmetric, and an effective electromotive force V (output voltage) can be extracted from the first terminal 51 and the second terminal 52.

  FIG. 11B shows a case where an external magnetic field H in the + Y direction is applied. In this case, the electromotive portion 30 </ b> D generates a first electromotive force V <b> 1 that goes from the first terminal 51 to the second terminal 52, and the electromotive portion 30 </ b> C has a second electromotive force that goes from the second terminal 52 to the first terminal 51. V2 is generated. Therefore, as in the case of FIG. 9B described above, the first electromotive force V1 and the second electromotive force V2 cancel each other, and the electromotive force V (output voltage) between the first terminal 51 and the second terminal 52 is almost equal. It becomes zero.

  Thus, the electromotive layer 30 shown in FIG. 10 has high sensitivity to the magnetic field component in the X direction. By rotating 90 degrees in the XY plane, it is also possible to realize the electromotive layer 30 having high sensitivity to the magnetic field component in the Y direction. In any case, the “effective length” of the electromotive layer 30 is increased by devising the planar pattern. Thereby, improvement in measurement sensitivity is realized without increasing the element area.

  Note that the plane pattern of the electromotive layer 30 is not limited to that shown in FIG. The electromotive layer 30 may be formed so that the first electromotive force V1 and the second electromotive force V2 are asymmetric when an external magnetic field H in a specific direction is applied to the element.

  For example, a planar pattern of the electromotive layer 30 as shown in FIG. 12 is possible. A “spiral” plane pattern as shown in FIG. 13 is also possible. In the example shown in FIG. 13, electromotive parts 30E and 30F having different spin orbit interactions (spin Hall effect) are mixed. A “meandering” planar pattern as shown in FIG. 14 is also possible. In the example shown in FIG. 14, electromotive portions 30G and 30H having different spin orbit interactions (spin Hall effect) are mixed. In any case, when the external magnetic field H in the X direction is applied, the first electromotive force V1 and the second electromotive force V2 become asymmetric.

5. Fifth Embodiment In the fifth embodiment of the present invention, it is considered that the magnetic field information DH is generated for each of the magnetic field components in different directions, based on the fourth embodiment. Specifically, the magnetic field information generation unit 40, the first terminal 51, the second terminal 52, and the electromotive layer 30 are considered as one set for detecting a magnetic field component in a specific direction. Such a set is provided for each different magnetic field component.

  For example, as illustrated in FIG. 15, an electromotive layer 30 </ b> X, an X-direction magnetic field information generation unit 40 </ b> X, a first terminal 51 </ b> X, and a second terminal 52 </ b> X are provided to detect a magnetic field component in the X direction. The electromotive layer 30X is configured to have high sensitivity to a magnetic field component in the X direction. A first terminal 51X and a second terminal 52X are formed at both ends of the electromotive layer 30X. The X-direction magnetic field information generation unit 40X is connected to the first terminal 51X and the second terminal 52X, and based on the information about the electromotive force V between the first terminal 51X and the second terminal 52X, the X-direction magnetic field information DH. -X is generated.

  Moreover, in order to detect the magnetic field component of a Y direction, the electromotive layer 30Y, the Y direction magnetic field information generation part 40Y, the 1st terminal 51Y, and the 2nd terminal 52Y are provided. The electromotive layer 30Y is configured to have high sensitivity to a magnetic field component in the Y direction. A first terminal 51Y and a second terminal 52Y are formed at both ends of the electromotive layer 30Y. The Y-direction magnetic field information generation unit 40Y is connected to the first terminal 51Y and the second terminal 52Y, and based on the information about the electromotive force V between the first terminal 51Y and the second terminal 52Y, the Y-direction magnetic field information DH. -Y is generated.

  In the example shown in FIG. 16, an electromotive layer 30X, an X-direction magnetic field information generation unit 40X, a terminal 51 (first terminal), and a terminal 52 (second terminal) are provided to detect a magnetic field component in the X direction. ing. The electromotive layer 30X is configured to have high sensitivity to a magnetic field component in the X direction. Terminals 51 and 52 are formed at both ends of the electromotive layer 30X. The X-direction magnetic field information generation unit 40X is connected to the terminals 51 and 52, and generates X-direction magnetic field information DH-X based on information on the electromotive force V between the terminals 51 and 52.

  Further, in order to detect a magnetic field component in the Y direction, an electromotive layer 30Y, a Y direction magnetic field information generation unit 40Y, a terminal 53 (first terminal), and a terminal 52 (second terminal) are provided. The electromotive layer 30Y is configured to have high sensitivity to a magnetic field component in the Y direction. Terminals 52 and 53 are formed at both ends of the electromotive layer 30Y. The Y-direction magnetic field information generation unit 40Y is connected to the terminals 52 and 53, and generates Y-direction magnetic field information DH-Y based on information on the electromotive force V between the terminals 52 and 53.

  In the example shown in FIG. 16, the electromotive layer 30X and the electromotive layer 30Y are connected, and the terminal 52 is shared by the X direction and the Y direction. Sharing terminals is preferable from the viewpoint of reducing the element area.

6). Sixth Embodiment With reference to FIGS. 17A and 17B, an application example of the magnetic field measurement apparatus 1 according to the embodiment of the present invention will be described. 17A and 17B show an electronic device 70 that can be opened and closed. The electronic device 70 includes a base portion 71 and a cover portion 72, and the electronic device 70 is opened and closed by rotating the cover portion 72.

  An upper permanent magnet 80 is attached to the cover portion 72. On the other hand, a lower permanent magnet 90 is attached to the base 71, and the magnetic field measuring apparatus 1 according to the embodiment of the present invention is provided on the lower permanent magnet 90 via a gap layer (buffer layer). It has been. Here, the magnetization direction of the upper permanent magnet 80 is the + Y direction, and the magnetization direction of the lower permanent magnet 90 is the -Y direction. Further, the magnetization of the upper permanent magnet 80 is larger than the magnetization of the lower permanent magnet 90.

  The electronic device 70 generates heat by operating, and the heat is applied to the magnetic field measuring apparatus 1. That is, the electronic device 70 (base portion 71) also serves as a heat source that applies a temperature gradient ∇T to the magnetic field measuring apparatus 1. In the example of FIGS. 17A and 17B, a temperature gradient ∇T in the + Z direction is applied to the magnetic field measuring apparatus 1.

  FIG. 17A shows the “open state”. In the open state, only the lower permanent magnet 90 exists in the vicinity of the magnetic layer 20. Therefore, the magnetization direction of the magnetic layer 20 is a direction corresponding to the local magnetic field created by the lower permanent magnet 90 (in this example, the + Y direction).

  FIG. 17B shows the “closed state”. In the closed state, the magnetic layer 20 is sandwiched between the lower permanent magnet 90 and the upper permanent magnet 80 and is affected by both. Here, since the magnetization of the upper permanent magnet 80 is larger than the magnetization of the lower permanent magnet 90, the influence from the upper permanent magnet 80 becomes dominant. Therefore, the magnetization direction of the magnetic layer 20 is a direction corresponding to the local magnetic field created by the upper permanent magnet 80 (in this example, the −Y direction).

  Thus, since the magnetization direction of the magnetic layer 20 is switched between the open state and the closed state, the direction of the electromotive force generated in the electromotive layer 30 is also switched. Therefore, it is possible to detect opening / closing of the electronic device 70 by referring to the magnetic field information DH output from the magnetic field information generation unit 40.

  As shown in this example, since the magnetic field measuring apparatus 1 can be operated using heat naturally generated in an electronic device or the like, a sensing system that does not require an external power supply and can be easily attached externally can be constructed.

7). Seventh Embodiment When the magnetic layer 20 has a hysteresis characteristic, magnetization may be initialized before measurement in order to increase measurement accuracy. The initialization of magnetization is performed by applying an initialization magnetic field from the outside using a permanent magnet or the like. The initialization magnetic field is stronger than the coercivity of the magnetic layer 20.

  For example, as shown in FIG. 18A, initialization is performed so that the magnetization state of the magnetic layer 20 becomes the saturation region RSA. After the initialization is completed, the magnetic field measurement is performed. In this case, the magnetic field information generation unit 40 generates the magnetic field information DH by referring to the voltage magnetic field characteristics CA.

  Further, for example, as shown in FIG. 18B, initialization may be performed so that the magnetization state of the magnetic layer 20 becomes the saturation region RSB. After the initialization is completed, the magnetic field measurement is performed. In this case, the magnetic field information generation unit 40 generates the magnetic field information DH by referring to the voltage magnetic field characteristics CB.

  Here, it should be noted that even when the same external magnetic field H is applied, the electromotive force V (output voltage) differs between FIG. 18A and FIG. 18B. Therefore, the voltage magnetic field characteristics (CA, CB) to be referred to may be switched according to the initialization method. Thereby, an accurate magnetic field measurement becomes possible.

  Further, as shown in FIG. 19, initialization may be performed by demagnetizing the magnetic layer 20 (making the magnetization zero). This also enables accurate magnetic field measurement. In addition, as a demagnetization method, thermal demagnetization in which magnetization is made zero by applying heat from the outside, or AC demagnetization in which magnetization is made zero by an external alternating magnetic field that decays with time can be used. In the case of thermal demagnetization, it is desirable to heat the magnetic layer 20 to the Curie temperature or higher.

  In actual magnetic field measurement, the spin Seebeck effect also changes depending on the temperature gradient applied to the element. Therefore, there is a possibility that the absolute value of the magnetic field cannot be accurately determined by measuring only the output voltage V. In this case, the output voltage Vs is measured in a state where the magnetization of the magnetic layer 20 is saturated with a saturation magnetic field, and a relative index (V / Vs) indicating how much the voltage is increased or decreased is evaluated. Since V and Vs are proportional to the temperature gradient, the temperature dependency is canceled by using the relative index, and the absolute value of the magnetic field can be determined.

  The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and can be appropriately changed by those skilled in the art without departing from the scope of the invention.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
A magnetic layer;
An electromotive layer formed on the magnetic layer and formed of a material that exhibits spin-orbit interaction;
A magnetic field measurement device comprising: a magnetic field information generation unit that generates magnetic field information related to a magnetic field applied to the magnetic layer based on information related to an electromotive force generated in the electromotive layer.

(Appendix 2)
A magnetic field measuring apparatus according to appendix 1, wherein
The magnetic material layer is a soft magnetic material.

(Appendix 3)
A magnetic field measuring apparatus according to appendix 1 or 2,
Furthermore,
A first terminal and a second terminal formed at different positions of the electromotive layer;
The magnetic field information generation unit is connected to the first terminal and the second terminal, and generates the magnetic field information based on information on the electromotive force between the first terminal and the second terminal. measuring device.

(Appendix 4)
The magnetic field measurement apparatus according to attachment 3, wherein
The electromotive force from the first terminal toward the second terminal is a first electromotive force,
The electromotive force from the second terminal toward the first terminal is a second electromotive force,
The electromotive layer is formed such that the first electromotive force and the second electromotive force are asymmetric when the magnetic field is applied in a specific direction.

(Appendix 5)
A magnetic field measuring apparatus according to appendix 4,
The electromotive layer is
A first electromotive part;
A first electromotive portion and a second electromotive portion formed of a material having a different spin Hall effect;
The magnetic field measurement apparatus in which the first electromotive force part generates the first electromotive force and the second electromotive force part generates the second electromotive force in a situation where the magnetic field is applied in the specific direction.

(Appendix 6)
A magnetic field measuring apparatus according to appendix 5, wherein
When considering the extending direction of each part of the electromotive layer when the electromotive layer is traced from the first terminal toward the second terminal,
The first electromotive portion includes a portion in which the extending direction is the first extending direction,
The second electromotive portion includes a portion in which the extending direction is a second extending direction antiparallel to the first extending direction.

(Appendix 7)
A magnetic field measuring apparatus according to any one of appendices 1 to 3,
The magnetic field measurement apparatus, wherein the magnetic field information generation unit is provided for each of the different directions so that the magnetic field information is generated for each of magnetic field components in different directions.

(Appendix 8)
The magnetic field measuring apparatus according to any one of appendices 4 to 6,
When considering the magnetic field information generation unit, the first terminal, the second terminal and the electromotive layer as one set,
The magnetic field measuring apparatus, wherein the set is provided for each different direction so that the magnetic field information is generated for each of magnetic field components in different directions.

(Appendix 9)
Providing a thermoelectric conversion element comprising: a magnetic layer; and an electromotive layer formed on the magnetic layer and formed of a material that exhibits spin-orbit interaction;
Generating magnetic field information relating to the magnetic field applied to the magnetic layer based on information relating to the electromotive force generated in the electromotive layer.

  This application claims the priority on the basis of the Japan patent application 2012-090459 for which it applied on April 11, 2012, and takes in those the indications of all here.

Claims (9)

A magnetic layer;
An electromotive layer formed on the magnetic layer and formed of a material that exhibits spin-orbit interaction;
A magnetic field measurement device comprising: a magnetic field information generation unit that generates magnetic field information related to a magnetic field applied to the magnetic layer based on information related to an electromotive force generated in the electromotive layer. The magnetic field measurement apparatus according to claim 1,
The magnetic material layer is a soft magnetic material. The magnetic field measuring device according to claim 1 or 2,
Furthermore,
A first terminal and a second terminal formed at different positions of the electromotive layer;
The magnetic field information generation unit is connected to the first terminal and the second terminal, and generates the magnetic field information based on information on the electromotive force between the first terminal and the second terminal. measuring device. The magnetic field measurement apparatus according to claim 3,
The electromotive force from the first terminal toward the second terminal is a first electromotive force,
The electromotive force from the second terminal toward the first terminal is a second electromotive force,
The electromotive layer is formed such that the first electromotive force and the second electromotive force are asymmetric when the magnetic field is applied in a specific direction. The magnetic field measurement apparatus according to claim 4,
The electromotive layer is
A first electromotive part;
A first electromotive portion and a second electromotive portion formed of a material having a different spin Hall effect;
The magnetic field measurement apparatus in which the first electromotive force part generates the first electromotive force and the second electromotive force part generates the second electromotive force in a situation where the magnetic field is applied in the specific direction. The magnetic field measuring apparatus according to claim 5,
When considering the extending direction of each part of the electromotive layer when the electromotive layer is traced from the first terminal toward the second terminal,
The first electromotive portion includes a portion in which the extending direction is the first extending direction,
The second electromotive portion includes a portion in which the extending direction is a second extending direction antiparallel to the first extending direction. A magnetic field measuring apparatus according to any one of claims 1 to 3,
The magnetic field measurement apparatus, wherein the magnetic field information generation unit is provided for each of the different directions so that the magnetic field information is generated for each of magnetic field components in different directions. The magnetic field measuring apparatus according to any one of claims 4 to 6,
When considering the magnetic field information generation unit, the first terminal, the second terminal and the electromotive layer as one set,
The magnetic field measuring apparatus, wherein the set is provided for each different direction so that the magnetic field information is generated for each of magnetic field components in different directions. Providing a thermoelectric conversion element comprising: a magnetic layer; and an electromotive layer formed on the magnetic layer and formed of a material that exhibits spin-orbit interaction;
Generating magnetic field information relating to the magnetic field applied to the magnetic layer based on information relating to the electromotive force generated in the electromotive layer.

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