Detection element and detection module

Abstract

To provide a detection element and detection module that can detect fluctuations in physical quantities with a relatively simple configuration. [Solution] The detection element comprises a detection unit that includes one or both of a magnetic metal and a magnetic semiconductor and has a breaking of spatial inversion symmetry due to magnetic order, and an output unit that outputs a fluctuation of a physical quantity in a direction orthogonal to the direction of the breaking of spatial inversion symmetry in the detection unit, which is the fluctuation of the physical quantity to be detected, as a detection signal.

Description

[Technical Field]

[0001] This disclosure relates to a detection element and a detection module. [Background technology]

[0002] Energy harvesting (environmental power generation) technology, which recovers various forms of energy from the surrounding environment and converts them into electrical energy, is attracting attention. Examples of such technologies include thermoelectric conversion elements utilizing the Seebeck effect, as described in Patent Document 1, and thermoelectric conversion elements utilizing the spin Seebeck effect, as described in Non-Patent Documents 1 and 2. Furthermore, detectors and sensors are known that detect malfunctions, accidents, or deterioration of objects (e.g., device failures, building deterioration, or health abnormalities in living organisms) by measuring specific physical quantities such as frequency, temperature, and current values ​​of a substance. For example, Patent Document 2 describes a fire detection device for detecting the occurrence of a fire. This fire detection device includes a microphone that collects sound generated in a monitoring area as acoustic data, a frequency analysis unit that calculates a frequency spectrum by frequency analysis of the acoustic data collected by the microphone, and a flame detection unit that determines whether or not 1 / f fluctuation characteristics are present in the frequency band below standing waves with respect to the frequency spectrum calculated by the frequency analysis unit, and detects that a flame has occurred in the monitoring area if it is determined that 1 / f fluctuation characteristics are present.

[0003] Devices that convert energy fluctuations into electrical energy are being researched. For example, Non-Patent Document 3 mentions Y3Fe5O 12 It has been disclosed that a multilayer device in which a MoGe film is stacked on top of a material has a second-order nonlinear thermoelectric conversion effect and can generate a voltage proportional to the square of the temperature gradient. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-144212 [Patent Document 2] Patent No. 7376660 [Non-patent literature]

[0005] [Non-Patent Document 1] Kenichi Uchida, Eiji Saito, "The Spin Seebeck Effect and its Application to Thermoelectric Conversion," Applied Physics, Japan Society of Applied Physics, 2013, Vol. 82, No. 11, pp. 928-931. [Non-Patent Document 2] K. Uchida, et. al., “Observation of the spin Seebeck effect”, Nature letters, 2008, Vol. 455, No. 9, p. 778-781 [Non-Patent Document 3] Hiroki Arisawa, Yuto Fujimoto1, Takashi Kikkawa, Eiji Saitoh, “Observation of nonlinear thermoelectric effect in MoGe / Y3Fe5O12”, Nature Communications, (2024)15:6912, https: / / doi.org / 10.1038 / s41467-024-50115-4 [Overview of the project] [Problems that the invention aims to solve]

[0006] Conventional thermoelectric devices utilizing the Seebeck effect and spin Seebeck effect convert a temperature gradient in an object into electrical energy. However, when the temperature gradient reverses, the polarity of the electric field generated within the device also reverses. Therefore, a steady temperature gradient was necessary for power generation. Consequently, it was practically impossible to perform thermoelectric conversion from a heat source where the direction and magnitude of the heat flow change randomly, i.e., from temperature fluctuations.

[0007] In addition, conventional detectors and sensors that detect failures, accidents, deterioration, etc. can only detect the occurrence of such problems after a failure, accident, or deterioration actually occurs in the object because of the mechanism of measuring physical quantities such as specific frequencies, temperatures, current values, etc. of substances. Therefore, it has not been possible to detect the signs of these problems and prevent their occurrence. If it were possible to detect the energy that repeats a certain regular movement, such as vibrations or electromagnetic noise emitted from the object, starting to move irregularly, it would be possible to detect signs of failures, accidents, deterioration, etc. of the object. For this purpose, it is necessary to detect the fluctuations in such energy that randomly change.

[0008] For the above reasons, research and development of elements that convert fluctuations in physical quantities such as the frequency of electromagnetic waves and vibrations, heat, current values, etc. into electrical energy are underway. However, conventional elements that can convert energy fluctuations into electrical energy have a laminated structure, a complex structure, and a complicated manufacturing process.

[0009] The present disclosure has been made in view of the above problems, and an object thereof is to provide a detection element and a detection module that can detect fluctuations in physical quantities with a relatively simple configuration.

Means for Solving the Problems

[0010] The inventors of the present disclosure have found that, with respect to the above problems, by using a magnetic metal and / or a magnetic semiconductor having a breakdown of spatial inversion symmetry due to magnetic order, it is possible to detect fluctuations in a physical quantity in a direction along the direction of the breakdown of spatial inversion symmetry in the magnetic metal and / or the magnetic semiconductor, and have thus completed the present disclosure. Therefore, the aspects of the present disclosure are as follows.

[0011] [1] A detection element including one or both of a magnetic metal and a magnetic semiconductor, having a breakdown of spatial inversion symmetry due to magnetic order, and an output unit that outputs, as a detection signal, fluctuations in a physical quantity in a direction orthogonal to the direction of the breakdown of spatial inversion symmetry in the detection unit, which are fluctuations in the physical quantity to be detected.

[0012] [2] The detection unit according to [1], which converts the fluctuation of the physical quantity into electrical energy.

[0013] [3] The detection unit according to [2], wherein the electrical energy is a non-reciprocal electrical signal.

[0014] [4] The detection unit according to [2], wherein the electrical energy is a non-linear electrical signal.

[0015] [5] The output unit has two or more electrodes, and the two or more electrodes are arranged at intervals along a direction orthogonal to the direction of the breakdown of the space inversion symmetry, according to any one of [1] to [4]. Detection element.

[0016] [6] Further, a magnetic field application unit that applies a magnetic field in a direction orthogonal to the direction of the breakdown of the space inversion symmetry, according to any one of [1] to [5]. Detection element.

[0017] [7] The detection unit according to any one of [1] to [6], which includes a magnetic metal or a magnetic semiconductor having any one of a three-fold symmetry, a four-fold symmetry, and a six-fold symmetry magnetic point group.

[0018] [8] The detection unit according to [7], which is four-fold symmetric and includes a magnetic metal or a magnetic semiconductor having a magnetic point group of a polar or odd-parity magnetic multipole.

[0019] [9] The detection unit according to [8], which includes a magnetic metal or a magnetic semiconductor that is a boride represented by the general formula RB4 (where R represents a lanthanoid or actinoid element) and has a magnetic point group of 4 / m’m’m’ or 4 / m’mm.

[0020]

[10] The detection unit according to [9], which includes TbB4 or GdB4 having a magnetic point group of 4 / m’m’m’ or NbB4 having a magnetic point group of 4 / m’mm.

[0021]

[11] The physical quantity is heat flow or electric current, the detection element according to any one of [1] to

[10] .

[0022]

[12] A detection module comprising multiple detection elements described in any one of [1] to

[11] .

[0023]

[13] The detection module according to

[12] , further comprising a storage unit for storing electrical energy. [Effects of the Invention]

[0024] This disclosure makes it possible to provide a detection element and a detection module that can detect fluctuations in physical quantities with a relatively simple configuration. [Brief explanation of the drawing]

[0025] [Figure 1] This is a perspective view showing a detection element according to one embodiment of the present disclosure. [Figure 2] This is a cross-sectional view of a detection element according to one embodiment of the present disclosure. [Figure 3] This is a process diagram illustrating the steps of a detection method according to one embodiment of the present disclosure, using thermoelectric conversion as an example. [Figure 4] This is a perspective view showing the configuration of a detection module using a detection element. [Figure 5] This is a schematic diagram illustrating an experimental method for measuring non-reciprocal detection signals. [Figure 6] This figure shows the measurement results from an experiment measuring non-reciprocal detection signals. [Modes for carrying out the invention]

[0026] The embodiments for implementing this disclosure will be described in detail below with reference to the attached drawings. In each drawing, the same reference numerals are used for the same elements where possible. Furthermore, the dimensional ratios within and between components in the drawings are arbitrary for the sake of readability.

[0027] Figure 1 is a perspective view showing a detection element according to one embodiment of the present disclosure, and Figure 2 is a cross-sectional view of the detection element according to one embodiment of the present disclosure.

[0028] As shown in Figures 1 and 2, the detection element 200 according to this embodiment is an element for detecting fluctuations in a physical quantity, and comprises a detection unit 202 and a pair of output units 207a and 207b that output fluctuations in the physical quantity to be detected as a detection signal.

[0029] In Figures 1 and 2, the Cartesian coordinate system C is shown, with the Z-axis set in the thickness direction of the detection unit 202, and the X-axis and Y-axis set in the direction of the long side and short side of the rectangle on the surface 202S of the detection unit 202, respectively. The Cartesian coordinate system C is also shown in subsequent figures as needed.

[0030] The detection unit 202 includes one or both of a magnetic metal and a magnetic semiconductor. The magnetic metal and magnetic semiconductor have a breaking of spatial inversion symmetry due to magnetic order. The magnetic metal has an electrical resistance of 1 × 10⁻¹⁰ -8 ~1 × 10 -4 Magnetic materials are within the range of Ωcm, and magnetic semiconductors have an electrical resistance of 1 × 10⁻⁶. -4 ~1 × 10 8 The magnetic material is within the range of Ωcm. The electrical resistance of the magnetic metal and magnetic semiconductor is the temperature at which the sensing element 200 is used. The sensing unit 202 is preferably composed of a magnetic material having highly symmetrical magnetic point groups with 3-fold, 4-fold, or 6-fold symmetry. Examples of magnetic point groups with 3-fold, 4-fold, and 6-fold symmetry are shown in Table 1 below. By including a magnetic material having these magnetic point groups, the non-reciprocity of conduction based on the breaking of spatial inversion symmetry of the sensing unit 202 becomes particularly large, and thus the conversion efficiency to a detection signal becomes particularly high.

[0031] [Table 1]

[0032] The detection unit 202 more preferably includes a magnetic metal or magnetic semiconductor that is four-fold symmetric and has a magnetic point group of polar or odd parity magnetic multipoles. Examples of magnetic point groups that are four-fold symmetric and have polar or odd parity magnetic multipoles are shown in Table 2 below.

[0033] [Table 2]

[0034] The most preferred embodiment of the detection unit 202 includes a boride represented by the general formula RB4 (where R represents a lanthanide or actinide element), in which the magnetic point group is 4 / m'm'm' or 4 / m'mm. The boride is preferably TB4, GdB4, or NbB4, in which the magnetic point group is 4 / m'm'm'.

[0035] The size and shape of the detection unit 202 can be any size and shape that can capture fluctuations in physical quantities, and can be designed to match the size and shape of available magnetic metals or magnetic semiconductors. For example, the detection unit 202 may be rectangular in shape, having a longer side along the X-axis and a shorter side along the Y-axis when viewed from above (i.e., from the Z-axis direction). The thickness of the detection unit 202 is not particularly limited, but can be, for example, between 1 nm and 1000 nm.

[0036] The detection unit 202 has a structure in which spatial inversion symmetry due to magnetic order is broken along the Z-axis direction. The detection unit 202 substantially has spatial inversion symmetry in the direction along the XY plane. Due to this breaking of spatial inversion symmetry along the Z-axis direction, the detection unit 202 exhibits non-reciprocity with respect to conductivity in the in-plane (XY plane) direction perpendicular to the Z-axis direction.

[0037] The magnetic metal and magnetic semiconductor included in the detection unit 202 may be paramagnetic or ferromagnetic. If the magnetic metal and magnetic semiconductor are paramagnetic, the detection element 200 may be equipped with a magnetic field application unit (not shown) that applies a magnetic field in a direction perpendicular to the direction of spatial inversion symmetry breaking (Z-axis direction) (Y-axis direction in Figure 1). By applying an external magnetic field B, a non-reciprocal or nonlinear detection signal can be generated in a direction perpendicular to the direction of spatial inversion symmetry breaking (Z-axis direction) and the direction of application of the external magnetic field B (Y-axis direction) (X-axis direction). If the magnetic metal and magnetic semiconductor are ferromagnetic (have magnetization in the Y-direction), the external magnetic field B may be unnecessary.

[0038] A pair of output units (e.g., electrodes) 207a and 207b are provided on the detection unit 202, spaced apart from each other in the in-plane direction (XY plane) of the detection unit 202. In the detection element 200 shown in Figure 1, the output units 207a and 207b are provided in the XY plane, but they can also be provided in the XZ plane or YZ plane as long as the detection signal can be detected. In this embodiment, the pair of output units 207a and 207b are made of a material having conductivity that allows for the extraction of a non-reciprocal detection signal from the detection unit 202, as described later. Examples of such materials include metallic materials such as Cu, Ag, Au, Pt, Ni, Al, constantan, Cr, In, Pd, Fe, Cu alloys, Ti / Au laminates, and Cr / Au laminates, conductive oxides such as indium tin oxide (ITO), and zinc oxide (ZnO). Cu, Ag, Au, Pt, Ni, Al, constantan, and Cu copper alloys are preferred, and Cu, Au, Ag, Pt, Ni, Ti / Au laminates, and Cr / Au laminates are particularly preferred.

[0039] The thickness of the pair of output sections 207a and 207b is not particularly limited, but can be, for example, 10 nm or more and 1 μm or less. The separation distance D207 between the pair of output sections 207a and 207b along the X-axis is preferably 0.1 μm or more and 1000 μm or less. Alternatively, the separation distance D207 can be designed taking into account the scale of spatial temperature fluctuations and the thermal diffusion of the magnetic metal.

[0040] The detection element 200 can be used, for example, as a thermoelectric conversion element that converts thermal fluctuations into electrical energy. In this case, the detection unit 202 functions as a thermoelectric conversion layer. The detection element 200 can also be used as a sensing element that detects the state of an object by converting fluctuations in physical quantities such as specific frequencies, temperatures, and current values ​​of electromagnetic waves and vibrations emitted from the object into electrical energy.

[0041] Next, a thermoelectric conversion method using the detection element 200 according to this embodiment as a thermoelectric conversion element will be described. Figure 3 is a process diagram showing the steps of the detection method according to this embodiment, with thermoelectric conversion as an example. As shown in Figure 3, the steps of the thermoelectric conversion method according to this embodiment include a step S11 of preparing the thermoelectric conversion element (detection element 200), a step S12 of inputting a heat flow, and a step S13 of performing thermoelectric conversion while applying an external magnetic field. These steps will be described again with reference to Figures 1 and 2.

[0042] In step S11, which involves preparing the thermoelectric conversion element, the aforementioned detection element 200 as shown in Figures 1 and 2 is prepared. Subsequently, in step S12, which involves inputting the heat flow, the flow (heat flow) H of an external physical quantity that is the target of thermoelectric conversion is input to the detection unit 202 so as to flow along the X-axis direction, which is one of the in-plane (XY plane) directions of the detection unit 202.

[0043] Next, in step S13, which performs thermoelectric conversion while applying an external magnetic field, an external magnetic field B generated from a magnetic field generator located outside the detection element 200 is applied to the detection unit 202. The direction in which the external magnetic field B is applied is in the in-plane (XY plane) direction of the detection element 200, and is the negative Y-axis direction, which is one of the directions perpendicular to the direction of the flow of the physical quantity (heat flow) H. As a result, the detection unit 202 is magnetized in the direction of the external magnetic field B and has magnetization oriented in the direction of the external magnetic field B. This application of the external magnetic field B is maintained while performing thermoelectric conversion of the physical quantity (heat flow) H. The magnitude of the external magnetic field B can be, for example, 9T or less. The temperature of the detection unit 202 may be, for example, 1K or more, and may include 300K or less.

[0044] The detection signal J generated within the detection unit 202 in this manner N becomes non-reciprocal with respect to the direction of the flow H of the physical quantity due to the non-reciprocal conduction of the detection unit 202 (i.e., the detection signal J N changes non-linearly with respect to the direction of the flow H of the physical quantity), and regardless of whether the direction of the flow H of the physical quantity is the positive X-axis direction or the negative X-axis direction, the direction of the detection signal J N is the positive X-axis direction, and the inventors of the present application have found that such a non-reciprocal detection signal J N can be taken out, for example, electrically through a pair of output units 207a and 207b. Therefore, according to the detection element 200 according to the present embodiment, even if the direction and magnitude of the flow H of the physical quantity change randomly, a non-reciprocal detection signal J in a constant direction can be generated within the detection unit 202 N so that it is possible to detect the fluctuation of the physical quantity on the microscale.

[0045] Also, by reversing the direction of the external magnetic field B to the positive Y-axis direction and reversing the magnetization direction of the detection unit 202 to the positive Y-axis direction, the direction of the non-reciprocal detection signal J N can be reversed to the negative X-axis direction.

[0046] In the detection unit 202, when the magnitude (e.g., voltage magnitude) of the non-reciprocal detection signal J N extracted by a pair of output units 207a and 207b is V, the field (e.g., electric field) generated within the detection unit 202 corresponding to V is E, the non-linear second-order coefficient (e.g., non-linear Seebeck coefficient) of the detection unit 202 is S, the distance between the pair of output units 207a and 207b is L (D207 in FIG. 2), the gradient of the physical quantity within the range of the distance L of the detection unit 202 is ∇T, and the difference in the physical quantity within the range of the distance L of the detection unit 202 is ΔT, the relationship of the field E = non-linear second-order coefficient S × (gradient of the physical quantity ∇T) 2 holds. By multiplying both sides of this equation by the distance L, the magnitude V of the non-reciprocal detection signal J N becomes V = non-linear second-order coefficient S × (difference in the physical quantity ΔT) 2 / L. Therefore, the smaller the distance L between the pair of output units 207a and 207b, the larger the non-reciprocal detection signal J NThe magnitude V becomes larger. Therefore, as described above, by making the separation distance D207 along the X-axis between the pair of output units 207a and 207b a small value of 1000 μm or less, the non-reciprocal detection signal J extracted by the pair of output units 207a and 207b becomes larger. N It gets bigger.

[0047] Furthermore, the sensing element 200 may include a conductive section provided so as to be in contact with or close to the end face on the positive X-axis side and / or the end face on the negative X-axis side, for facilitating the flow of the physical quantity H into the sensing unit 202. Such a conductive section can be made of, for example, aluminum, copper, carbon fiber, sapphire, alumina, silicon with a thermal oxide film, or a polymer.

[0048] Figure 4 is a perspective view showing the configuration of a detection module using the detection elements described above. As shown in Figure 4, the detection module 300 according to this embodiment comprises a plurality of detection elements 200, and in this embodiment, it has four detection elements 200a, 200b, 200c, and 200d. The four detection elements 200a, 200b, 200c, and 200d receive a non-reciprocal detection signal J from each detection unit. N They are connected to each other in such a way that they are of the same polarity and superimposed on one another.

[0049] Specifically, in the detection module 300, detection elements 200a and 200c, arranged with respect to the Cartesian coordinate system C in the same manner as the detection element 200 shown in Figures 1 and 2, and detection elements 200b and 200d, arranged with respect to the Cartesian coordinate system C in the same manner as the detection element 200 shown in Figures 1 and 2 rotated 180 degrees around the Y axis, are alternately provided along the Y-axis direction. That is, the detection elements 200a, 200b, 200c, and 200d are arranged such that the direction of spatial inversion symmetry breaking (Z-axis direction) of adjacent detection units is opposite, thus reversing their non-reciprocal directions. Furthermore, the output section 207a of detection element 200a and the output section 207b of detection element 200b are connected (e.g., electrically connected), the output section 207a of detection element 200b and the output section 207b of detection element 200c are connected, and the output section 207a of detection element 200c and the output section 207b of detection element 200d are connected. Alternatively, instead of arranging the detection elements 200b and 200d in a manner rotated 180 degrees around the Y-axis, the detection elements 200b and 200d can be arranged relative to the Cartesian coordinate system C in the same manner as the detection elements 200 shown in Figures 1 and 2, similar to the detection elements 200a and 200c, and then connected so that non-reciprocal detection signals of the same polarity can be superimposed on the detection elements 200b and 200d. In this case, the output section 207a of detection element 200a is connected to the output section 207a of detection element 200b, the output section 207b of detection element 200b is connected to the output section 207b of detection element 200c, and the output section 207a of detection element 200c is connected to the output section 207a of detection element 200d.

[0050] Furthermore, the detection parts of the four detection elements 200a, 200b, 200c, and 200d are magnetized in the negative Y-axis direction by the external magnetic field B, and have a magnetization 203M oriented in the negative Y-axis direction.

[0051] Furthermore, the detection module 300 includes physical quantity collection units (e.g., heat conduction units) 301 and 302 provided so as to be in contact with or close to the negative X-axis end faces and positive X-axis end faces of the four detection elements 200a, 200b, 200c, and 200d. This makes it easier for physical quantities (e.g., heat flow, electric current) flowing in the X-axis direction to flow into the ferromagnetic metal layers 203 of each of the four detection elements 200a, 200b, 200c, and 200d. The detection module 300 does not necessarily have to include the physical quantity collection units 301 and 302.

[0052] Since physical quantities flow into the ferromagnetic metal layers 203 of each of the four detection elements 200a, 200b, 200c, and 200d, and the non-reciprocal detection signals generated by each detection element 200 are superimposed with the same polarity, they can then be extracted by the output section 207b of detection element 200a and the output section 207a of detection element 200d, making it possible to extract a large detection signal. [Examples]

[0053] Next, to further clarify the effects of this disclosure, we will explain them using examples.

[0054] (TB4 synthesis) Tb (shot, 3-4 mm), B (lump), and flux Al are weighed in an elemental ratio of Tb:B:Al = 1:4:85 and packed into a Tammann tube. The Tammann tube is heated from room temperature to 300°C in 2 hours under argon gas flow and held at 300°C for 2 hours. The temperature is further increased to 1500°C over 12 hours and held at 1500°C for 10 hours. After that, it is slowly cooled to 600°C at 5°C / Hr and then cooled from 600°C to room temperature over 5 hours. The ingot removed from the Tammann tube is immersed in NaOH aqueous solution and HCl aqueous solution to remove residual flux (Al). By removing the flux, single crystal TB4 is obtained from the ingot.

[0055] (Fabrication of sensing element) Using the TB4 obtained in the above TB4 synthesis example, a detection unit 202 with a width of 3 mm in the Y-axis direction and a length of 5 mm in the X-axis direction was obtained. Subsequently, a pair of electrodes corresponding to a pair of output units 207a and 207b were formed on the detection unit 202 to fabricate a detection element corresponding to the detection element 200.

[0056] (Evaluation of the detection element) Next, the detection element undergoes a process S12 in which heat flow is input and a process S13 in which thermoelectric conversion is performed while an external magnetic field is applied, and a non-reciprocal detection signal J is output from a pair of output units 207a and 207b. N An experiment was conducted to measure the non-reciprocal detection signal J. Figure 5 shows the non-reciprocal detection signal J. N This is a schematic diagram showing an experimental method for measuring [the signal]. As shown in Figure 5, a first resistance heater 210 is provided adjacent to the negative X-axis end of the element corresponding to the sensing element 200, and a second resistance heater 211 is provided adjacent to the positive X-axis end of the element. The first resistance heater 210 and the second resistance heater 211 are electrically connected to the first power supply 220 and the second power supply 221, respectively. A lock-in amplifier 230 is electrically connected between the pair of output units 207a and 207b.

[0057] Then, while varying the magnitude of the external magnetic field B applied to the detection element 200 in the negative Y-axis direction from 9T to -9T, the first resistance heater 210 changes the AC temperature gradient ΔT in a sinusoidal manner with angular frequency ω in the direction along the X-axis relative to the detection element 200. AC And, among the detection signals generated by the detection element 200, the AC temperature gradient ΔT AC ΔV is the y component of the change in the detection signal corresponding to twice the frequency. 2ω、y This was detected by the lock-in amplifier 230.

[0058] AC temperature gradient ΔT AC More specifically, when ω is the angular frequency and t is time, the first power supply 220 supplies V to the first resistance heater 210. dc +V ac An AC voltage of sin(ωt) was applied to the sensing element 200 in the direction along the X-axis.AC =(√2)ΔT rms An AC temperature gradient expressed as sin(ωt) is applied (ΔT rms (wherein this is the effective value of the AC temperature gradient). A voltage source device WF1968 manufactured by NF Circuit Design Block Co., Ltd. was used as the first power supply 220 and the second power supply 221, and a lock-in amplifier LI5640 manufactured by NF Circuit Design Block Co., Ltd. was used as the lock-in amplifier 230. In addition, the frequency f (=ω / 2π) of the above AC voltage applied by the first power supply 220 was set to 3.7 Hz.

[0059] Figure 6 shows the detection signal ΔV obtained as a result of the above experiment. 2ω、y This figure shows the dependence of the external magnetic field B on the detection element 200. The sinusoidally changing ΔT is applied to the detection element 200. AC This corresponds to temperature fluctuations at the microscale. And if the detection signal output from the detection element 200 is the AC temperature gradient ΔT AC When the polarity is nonlinear (non-reciprocal), the detection signal ΔV 2ω、y It will have a finite value.

[0060] In this experiment, as shown in Figure 6, when an external magnetic field B is applied, ΔV has a finite value. 2ω、y When detected, and the polarity of the external magnetic field B reverses, ΔV 2ω、y The polarity of the signal was also reversed. This demonstrated that the sensing element used in this experiment can generate a detection signal nonlinearly with respect to the direction of the temperature gradient, making it possible to perform thermoelectric conversion from temperature fluctuations at the microscale where a temperature gradient is virtually nonexistent at the macroscale.

[0061] In this experiment, the first power supply 220 and the second power supply 221 are connected to the detection element 200 fabricated in this experiment, instead of the first and second resistance heaters. Then, by applying an external magnetic field B in the negative Y-axis direction to the detection element 200 and applying an AC current gradient to the detection element 200 instead of an AC temperature gradient, it is possible to convert current fluctuations into a nonlinear electrical signal.

[0062] This disclosure is not limited to the embodiments described above, and various modifications are possible.

[0063] For example, in the embodiment described above, the detection unit 202 of the detection element 200 is a self-supporting layer, but a substrate may be placed on the surface 202S opposite to the output units 207a and 207b of the detection unit 202.

[0064] Furthermore, in the above-described embodiment, the external magnetic field B is applied in the in-plane direction (in the XY plane) of the detection element 200 and perpendicular to the direction of the flow of the physical quantity H (see Figures 1 and 2). However, it may also be applied in the in-plane direction (in the XY plane) of the detection element 200 and intersect the direction of the flow of the physical quantity H at an angle other than 90 degrees. However, the external magnetic field B and the flow of the physical quantity H are set so that they are neither parallel nor antiparallel to each other.

[0065] Embodiments of this disclosure are described below.

[0066] [Note 1] A detection element comprising: a detection unit containing one or both of a magnetic metal and a magnetic semiconductor, having a breaking of spatial inversion symmetry due to magnetic order; and an output unit that outputs fluctuations of a physical quantity in a direction orthogonal to the direction of the breaking of spatial inversion symmetry in the detection unit, as a detection signal. According to the detection element in Appendix 1, even if the detection unit has a simple configuration containing one or both of a magnetic metal and a magnetic semiconductor, fluctuations of a physical quantity in a direction orthogonal to the direction of the breaking of spatial inversion symmetry in the detection unit can be detected.

[0067] [Note 2] The detection unit is a detection element described in Appendix 1 that converts fluctuations in the physical quantity into electrical energy. With the detection element described in Appendix 2, fluctuations in the physical quantity are converted into electrical energy, so fluctuations in the physical quantity can be detected as an electrical signal.

[0068] [Note 3] The aforementioned electrical energy is a non-reciprocal electrical signal, as described in Appendix 2. According to the detection element in Appendix 3, since the electrical energy is a non-reciprocal electrical signal and the flow of electrical energy in the detection unit in response to fluctuations in the physical quantity is unidirectional, fluctuations in the physical quantity can be detected even if they are alternating current.

[0069] [Note 4] The aforementioned electrical energy is a nonlinear electrical signal, as described in Appendix 2. According to the detection element in Appendix 4, it is possible to generate electrical energy with a voltage proportional to the square of the gradient of the fluctuation of the physical quantity, thus allowing a large amount of electrical energy to be obtained from the fluctuation of the physical quantity.

[0070] [Note 5] The output unit has two or more electrodes, and each of the two or more electrodes is spaced apart along a direction perpendicular to the direction of the breaking of spatial inversion symmetry, as described in any one of Appendices 1 to 4. According to the detection unit of Appendice 5, since each of the two or more electrodes is spaced apart along a direction perpendicular to the direction of the breaking of spatial inversion symmetry of the detection unit, the detection signal can be efficiently extracted to the outside.

[0071] [Note 6] Furthermore, the detection element according to any one of the appendices 1 to 5 comprises a magnetic field application unit that applies a magnetic field in a direction perpendicular to the direction of the breaking of spatial inversion symmetry. According to the detection element of appendice 6, since the magnetic field is applied in a direction perpendicular to the direction of the breaking of spatial inversion symmetry of the detection unit, the conversion efficiency from fluctuations in physical quantities to detection signals is further increased.

[0072] [Note 7] The detection unit is a detection element according to any one of 1 to 6, comprising a magnetic metal or magnetic semiconductor having a magnetic point group that is 3-fold symmetric, 4-fold symmetric, or 6-fold symmetric. According to the detection element in Appendix 7, the non-reciprocity of conduction due to the breaking of spatial inversion symmetry in the detection unit becomes larger, thus increasing the conversion efficiency to a thermoelectric detection signal.

[0073] [Note 8] The detection unit is a detection element as described in Appendix 7, which is four-fold symmetric and includes a magnetic metal or magnetic semiconductor having a group of magnetic points of polar or odd parity magnetic multipoles. With the detection element of Appendix 8, the non-reciprocity of conduction due to the breaking of spatial inversion symmetry of the detection unit becomes greater, and the conversion efficiency to a thermoelectric detection signal becomes higher.

[0074] [Note 9] The detection unit includes a detection element as described in Appendix 8, which is a magnetic metal or magnetic semiconductor that is a boride with a magnetic point group of 4 / m'm'm' or 4 / m'mm and whose general formula is RB4 (where R represents a lanthanide or actinide element). With the detection element of Appendix 9, the non-reciprocity of conduction due to the breaking of spatial inversion symmetry in the detection unit becomes even greater, thus further increasing the conversion efficiency to a thermoelectric detection signal.

[0075] [Note 10] The detection unit includes the detection element described in Appendix 9, which includes TbB4 or GdB4 with a magnetic point group of 4 / m'm'm' or NbB4 with a magnetic point group of 4 / m'mm. With the detection element described in Appendix 10, the non-reciprocity of conduction due to the breaking of spatial inversion symmetry in the detection unit becomes particularly large, resulting in a particularly high conversion efficiency to a thermoelectric detection signal.

[0076] [Note 11] The aforementioned physical quantity is either heat flow or electric current, as described in one of the detection elements in Appendix 1 to 10. According to the detection element in Appendix 11, fluctuations in heat flow or electric current can be detected.

[0077] [Note 12] A detection module comprising multiple detection elements described in any one of the appendices 1 to 11. According to the detection module in appendice 12, since it comprises multiple of the above-mentioned detection elements, a larger detection signal can be obtained. In addition, fluctuations in physical quantities can be detected over a wider range.

[0078] [Note 13] Furthermore, the detection module described in Appendix 12 has a storage unit for storing electrical energy. According to the detection module described in Appendix 13, since the detection signal can be stored as electrical energy, the detection module can be used as a power generation device or a storage battery.

[0079] [Note 14] A thermoelectric conversion element comprising: a thermoelectric conversion unit containing one or both of a magnetic metal and a magnetic semiconductor, having spatial inversion symmetry breaking due to magnetic order; and an output unit that outputs fluctuations in heat flow in a direction perpendicular to the direction of spatial inversion symmetry breaking in the thermoelectric conversion unit as a detection signal. According to the thermoelectric conversion element of Appendix 14, even if the thermoelectric conversion unit has a simple configuration containing one or both of a magnetic metal and a magnetic semiconductor, fluctuations in heat flow in a direction perpendicular to the direction of spatial inversion symmetry breaking in the thermoelectric conversion unit can be converted into a thermoelectric signal. The inventors of this invention have found that with this thermoelectric conversion element, the thermoelectric signal generated in the thermoelectric conversion unit by the incoming heat flow is non-reciprocal with respect to the direction of the heat flow due to non-reciprocal conduction in the thermoelectric conversion unit, and such a non-reciprocal thermoelectric signal can be electrically extracted by a pair of electrodes. Therefore, even from a heat flow whose direction and magnitude change randomly, it is possible to generate a thermoelectric signal in a constant direction within the thermoelectric conversion unit, making it possible to perform thermoelectric conversion from temperature fluctuations on a microscale.

[0080] [Note 15] A thermoelectric conversion method comprising the steps of preparing a thermoelectric conversion element as described in Appendix 14, and inputting a heat flow to the thermoelectric conversion unit. According to the thermoelectric conversion method of Appendix 15, since the thermoelectric conversion element described in Appendix 14 is used, it becomes possible to perform thermoelectric conversion from temperature fluctuations on a microscale.

[0081] [Note 16] Furthermore, the thermoelectric conversion method described in Appendix 15 includes a step of performing thermoelectric conversion while applying an external magnetic field in a direction perpendicular to the direction of spatial inversion symmetry breaking in the thermoelectric conversion section. According to the thermoelectric conversion method of Appendix 16, when a heat flow flows into a magnetic metal and / or magnetic semiconductor that breaks spatial inversion symmetry due to magnetic order, a thermoelectric signal is generated in the direction along the heat flow. The thermoelectric signal generated in the magnetic metal and / or magnetic semiconductor that breaks spatial inversion symmetry due to magnetic order is non-reciprocal with respect to the direction of the heat flow due to non-reciprocal conduction of the thermoelectric conversion layer, and such a non-reciprocal thermoelectric signal can be electrically extracted by a pair of output units. Therefore, even from a heat flow whose direction and magnitude change randomly, it is possible to generate a thermoelectric signal in a constant direction within the magnetic metal / semiconductor that breaks spatial inversion symmetry due to magnetic order, making it possible to perform thermoelectric conversion from temperature fluctuations on a microscale.

[0082] [Note 17] The thermoelectric conversion method described in Appendix 15, wherein the temperature of the thermoelectric conversion unit is in the range of 1K to 300K in the process of performing thermoelectric conversion while applying an external magnetic field. In the thermoelectric conversion method described in Appendix 16, the temperature of the thermoelectric conversion unit is in the range of 50K to 300K, so the thermoelectric conversion efficiency is improved. [Explanation of Symbols]

[0083] 200...Detection element, 202...Detection unit, 207a, 207b...Output unit

Claims

1. A detection unit comprising one or both a magnetic metal and a magnetic semiconductor, and having a breaking of spatial inversion symmetry due to magnetic order, A detection element comprising: an output unit that outputs a detection signal of fluctuations in a physical quantity that are to be detected, which are fluctuations in a direction orthogonal to the direction of spatial inversion symmetry breaking in the detection unit; and an output unit that outputs fluctuations in the physical quantity to be detected.

2. The detection element according to claim 1, wherein the detection unit converts fluctuations in the physical quantity into electrical energy.

3. The detection element according to claim 2, wherein the electrical energy is a non-reciprocal electrical signal.

4. The detection element according to claim 2, wherein the electrical energy is a nonlinear electrical signal.

5. The output unit has two or more electrodes, The detection element according to claim 1 or 2, wherein the two or more electrodes are each spaced apart along a direction orthogonal to the direction of the breaking of spatial inversion symmetry.

6. Furthermore, the detection element according to claim 1 or 2, further comprising a magnetic field application unit that applies a magnetic field in a direction perpendicular to the direction of the breaking of spatial inversion symmetry.

7. The detection element according to claim 1 or 2, wherein the detection unit includes a magnetic metal or magnetic semiconductor having a magnetic point group that is 3-fold symmetric, 4-fold symmetric, or 6-fold symmetric.

8. The detection element according to claim 7, wherein the detection unit is four-fold symmetric and includes a magnetic metal or magnetic semiconductor having a magnetic point group of polar or odd parity magnetic multipoles.

9. The detection unit has a magnetic point group of 4 / m'm'm' or 4 / m'mm, and the general formula is RB ４ The detection element according to claim 8, comprising a magnetic metal or magnetic semiconductor which is a boride represented by (wherein R represents a lanthanide or actinide element).

10. The detection unit has a magnetic point cloud of 4 / m'm'm' TbB ４ or GdB ４ Alternatively, NbB where the magnetic point group is 4 / m'mm ４ The detection element according to claim 9, including the above.

11. The detection element according to claim 1 or 2, wherein the physical quantity is heat flow or electric current.

12. A detection module comprising a plurality of detection elements as described in claim 1 or 2.

13. Furthermore, the detection module according to claim 12, further comprising a storage unit for storing electrical energy.

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