Fluctuation detection sensor

Abstract

To provide a sensor capable of detecting micro-scale energy fluctuation emitted from an object.SOLUTION: The fluctuation detection sensor 200 of the present invention includes a nonlinear response layer 202 having a nonlinear electrical response characteristic with respect to input of external energy along a first direction, and a pair of electrodes 207a and 207b for extracting an electrical response signal generated in the nonlinear response layer 202 due to energy fluctuation input from the outside along the first direction to the nonlinear response layer 202.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fluctuation detection sensor. [Background technology]

[0002] There are known detectors and sensors that detect failures, accidents, deterioration, etc. of objects (for example, device failures, building deterioration, or abnormalities in the health of living organisms) by measuring physical quantities such as specific frequencies, temperatures, or current values ​​of substances. For example, Patent Document 1 describes a fire detection device that detects the outbreak of a fire. This fire detection device includes a microphone that collects sounds generated in a monitored area as acoustic data, a frequency analysis unit that calculates a frequency spectrum by frequency-analyzing the acoustic data collected by the microphone, and a flame detection unit that determines whether the frequency spectrum calculated by the frequency analysis unit contains 1 / f fluctuation characteristics in a frequency band below standing waves, and detects the outbreak of a flame in the monitored area if it is determined that the 1 / f fluctuation characteristics are contained. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7376660 specification Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional detectors and sensors for detecting breakdowns, accidents, deterioration, etc., measure physical quantities such as specific frequencies, temperatures, and current values ​​of materials, and therefore can only detect the occurrence of breakdowns, accidents, or deterioration once they actually occur in the target object. Therefore, they are unable to detect the signs of these events and prevent them from occurring. It is believed that if energy such as vibrations and electromagnetic noise emitted from a target object, which normally repeats a certain regular pattern, can be detected to begin to move irregularly, it will be possible to detect the signs of breakdowns, accidents, or deterioration of the target object. However, to do this, it is necessary to detect fluctuations in such energy that change randomly on a microscale. However, no sensor capable of detecting microscale energy fluctuations emitted from such targets has been known until now.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a sensor capable of detecting micro-scale energy fluctuations emitted from an object. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, the fluctuation detection sensor of the present invention comprises a nonlinear response unit having a nonlinear electrical response characteristic to the input of external energy along a first direction, and an electrode unit for extracting an electrical response signal generated in the nonlinear response unit due to energy fluctuations input from the outside to the nonlinear response unit along the first direction.

[0007] The inventors have found that, with the fluctuation detection sensor according to the present invention, the electrical response signal generated in the nonlinear response unit by energy fluctuations input from outside is nonreciprocal with respect to the direction of energy flow due to the nonlinear electrical response characteristics of the nonlinear response unit, and that such a nonreciprocal electrical response signal can be electrically extracted by the electrode unit. Therefore, even from external energy whose direction and magnitude change randomly, it is possible to generate a nonlinear voltage signal, which is an electrical response signal that is nonreciprocal in a fixed direction, within the nonlinear response unit, making it possible to detect microscale energy fluctuations emitted from an object.

[0008] Furthermore, in the fluctuation detection sensor according to the present invention, the external energy can be an electric current and / or a heat flow, and the energy fluctuation can be an electric current fluctuation and / or a heat flow fluctuation, in which case it becomes possible to detect an electric current fluctuation and / or a heat flow fluctuation emitted from an object.

[0009] Furthermore, in the fluctuation detection sensor according to the present invention, the external energy can be a current and the energy fluctuation can be a current fluctuation, in which case it is possible to detect a current fluctuation emitted from an object.

[0010] Furthermore, in the fluctuation detection sensor according to the present invention, the nonlinear response section can have a configuration in which spatial inversion symmetry is broken along a second direction orthogonal to the first direction.

[0011] Furthermore, in the fluctuation detection sensor according to the present invention, the nonlinear response section can include a ferromagnetic layer and a paramagnetic layer stacked on top of each other along the second direction.

[0012] Furthermore, in the fluctuation detection sensor according to the present invention, the ferromagnetic layer can be configured to have spontaneous magnetization and / or high coercive force.

[0013] Furthermore, in the fluctuation detection sensor according to the present invention, the ferromagnetic layer may be a ferromagnetic metal layer made of an L10 ordered alloy of a magnetic metal and a paramagnetic metal, and the paramagnetic layer may be a paramagnetic metal layer, thereby increasing the coercive force of the ferromagnetic layer. [Effects of the Invention]

[0014] According to the present invention, a sensor capable of detecting micro-scale energy fluctuations emitted from an object is provided. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing a fluctuation detection sensor according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the fluctuation detection sensor according to the embodiment. [Figure 3] 1 is a process diagram showing steps of an energy conversion method according to an embodiment. [Figure 4] FIG. 1 is a perspective view showing the configuration of a fluctuation detection sensor module using a fluctuation detection sensor. [Figure 5] 1 is a schematic diagram showing an experimental method for measuring a non-reciprocal voltage signal JN in Example 1. FIG. [Figure 6] FIG. 1 is a diagram showing the measurement results of the experiment in Example 1. [Figure 7] FIG. 10 is a schematic diagram showing an experimental method for measuring a non-reciprocal voltage signal JN in Example 2. [Figure 8] FIG. 10 is a diagram showing the measurement results of the experiment in Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In each drawing, the same reference numerals are used for the same elements where possible. Furthermore, the dimensional ratios within and between elements in the drawings are arbitrary for ease of viewing.

[0017] FIG. 1 is a perspective view showing a fluctuation detection sensor according to an embodiment, and FIG. 2 is a cross-sectional view of the fluctuation detection sensor according to an embodiment.

[0018] As shown in FIGS. 1 and 2, a fluctuation detection sensor 200 according to this embodiment includes a substrate 201, a nonlinear response layer 202 as a nonlinear response section, and a pair of electrodes 207a and 207b as an electrode section.

[0019] The substrate 201 is a plate- or film-shaped member, for example, as shown in Fig. 1, and has a substantially flat surface 201S. The surface 201S is rectangular when viewed from the Z-axis direction, for example, as shown in Fig. 1. The substrate 201 is a member for laminating a nonlinear response layer 202 on the surface 201S. Examples of materials that can be used to form the substrate 201 include metals such as Au, Ag, Cu, and Al, silicon, sapphire, SiC, GaN, yttria-stabilized zirconia (YSZ), and resins such as polyimide, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN).

[0020] 1 and 2 show a Cartesian coordinate system C, with the Z axis set in the thickness direction of the substrate 201 and the X and Y axes set in the long and short side directions, respectively, of the rectangle of the surface 201S of the substrate 201. The Cartesian coordinate system C is also shown in the subsequent figures as needed.

[0021] The nonlinear response layer 202 has a nonlinear electrical response characteristic to the input of external energy along the X-axis direction, which is a first direction. The external energy is, for example, an electric current and / or a heat flow. In this embodiment, the nonlinear response layer 202 includes a ferromagnetic layer 203 and a paramagnetic layer 205 stacked along the Z-axis direction, which is a second direction. The ferromagnetic layer 203 is stacked on the substrate 201, and the paramagnetic layer 205 is stacked on the ferromagnetic layer 203. The ferromagnetic layer 203 is made of a material that exhibits ferromagnetism at temperatures in the environment in which the fluctuation detection sensor 200 is used, and is preferably made of a material that exhibits ferromagnetism at room temperature (300 K). In this embodiment, the ferromagnetic layer 203 is made of a hard magnetic material and may have spontaneous magnetization 203M. In addition, the ferromagnetic layer 203 preferably has a high coercive force, for example, a coercive force of 50 mT or more.

[0022] Furthermore, the ferromagnetic layer 203 is preferably a ferromagnetic metal layer. The ferromagnetic metal layer is preferably made of an L10-type ordered alloy consisting of a magnetic metal that exhibits ferromagnetism at room temperature (300 K) and a paramagnetic metal that exhibits paramagnetism. The magnetic metal is preferably made of at least one of iron, nickel, cobalt, gadolinium, dysprosium, and terbium, and the paramagnetic metal is preferably made of Pt, Pd, W, an AuW alloy, Ta, a CuIr alloy, a CuBi alloy, a BiSb alloy, or a BiSe alloy. By making the ferromagnetic layer 203 of such an L10-type ordered alloy, the ferromagnetic layer 203 can have a particularly large coercive force, allowing the fluctuation detection sensor 200, described below, to efficiently convert energy from current fluctuations and / or heat flow fluctuations at room temperature and in a magnetic field-free environment.

[0023] The nonlinear response layer 202 has, for example, a rectangular shape in plan view (i.e., when viewed from the Z-axis direction) with a long side along the X-axis direction and a short side along the Y-axis direction. The thickness of the ferromagnetic layer 203 is not particularly limited, but can be, for example, 1 nm or more and 100 nm or less.

[0024] The paramagnetic layer 205 is made of a material that exhibits paramagnetism at the temperature of the environment in which the fluctuation detection sensor 200 is used, and is preferably made of a material that exhibits paramagnetism at room temperature (300 K). The paramagnetic layer 205 is also preferably a paramagnetic metal layer. The paramagnetic metal layer is preferably made of a paramagnetic metal with high spin-orbit interaction to enhance the spin-Nernst effect and spin-Hall effect within the paramagnetic metal layer, as described below. From this perspective, the paramagnetic layer is preferably made of Pt, Pd, W, an AuW alloy, Ta, a CuIr alloy, a CuBi alloy, a BiSb alloy, or a BiSe alloy, and is particularly preferably made of Pt. The thickness of the paramagnetic layer 205 is not particularly limited, but can be, for example, 1 nm or more and 100 nm or less.

[0025] In this embodiment, the nonlinear response layer 202 exhibits nonreciprocal conduction due to the breaking of spatial inversion symmetry. Specifically, a paramagnetic layer is provided on the surface of the ferromagnetic layer 203, but a similar paramagnetic layer is not provided on the back surface of the ferromagnetic layer 203. Also, a ferromagnetic layer is provided on the back surface of the paramagnetic layer 205, but a similar ferromagnetic layer is not provided on the front surface of the paramagnetic layer 205. Therefore, the nonlinear response layer 202 has a structure in which spatial inversion symmetry is broken along the Z-axis direction. The nonlinear response layer 202 has substantial spatial inversion symmetry in the direction along the XY plane. The nonlinear response layer 202 of this embodiment exhibits nonreciprocity in the in-plane (XY plane) electrical conductivity due to the breaking of spatial inversion symmetry along the Z-axis direction.

[0026] The pair of electrodes 207a, 207b are provided on the nonlinear response layer 202 and spaced apart from each other in the in-plane (XY plane) direction of the nonlinear response layer 202. In this embodiment, the pair of electrodes 207a, 207b are provided on the paramagnetic layer 205 so as not to contact the ferromagnetic layer 203, and are provided on the surface 205S of the paramagnetic layer 205 opposite to the ferromagnetic layer 203. The pair of electrodes 207a, 207b are spaced apart from each other along the X-axis direction, which is one of the in-plane (XY plane) directions of the paramagnetic layer 205.

[0027] The pair of electrodes 207a, 207b are made of a material having conductivity that allows a non-reciprocal voltage signal to be extracted from the nonlinear response layer 202, as described below. Examples of such materials include metal materials such as Cu, Ag, Au, Pt, Ni, Al, constantan, Cr, In, Pd, Fe, Cu alloys, Ti / Au stacks, and Cr / Au stacks, and 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 stacks, and Cr / Au stacks are particularly preferred.

[0028] The thickness of the pair of electrodes 207a, 207b is not particularly limited, but may be, for example, 10 nm or more and 1 μm or less. The separation distance D207 between the pair of electrodes 207a, 207b along the X-axis direction is preferably 0.1 μm or more and 1000 μm or less.

[0029] Furthermore, the fluctuation detection sensor 200 of this embodiment may further include a layer made of an electrically insulating magnetic material that is provided so as to be in contact with the ferromagnetic layer 203, or may not include such a layer.

[0030] When manufacturing such a fluctuation detection sensor 200, for example, a substrate 201 is prepared, and a material for forming the ferromagnetic layer 203 and a material for forming the paramagnetic layer 205 are deposited in this order on the surface 201S of the substrate by physical vapor deposition such as DC magnetron sputtering to form a laminate, and the laminate is patterned into a rectangular shape in plan view by photolithography and lift-off to form the nonlinear response layer 202. Thereafter, a metal material for forming the pair of electrodes 207a, 207b is deposited in a region including the surface 205S of the paramagnetic layer 205 by physical vapor deposition such as DC magnetron sputtering to form a metal layer, and the metal layer is patterned into a predetermined shape by photolithography and lift-off to form the pair of electrodes 207a, 207b.

[0031] Next, the energy conversion method according to this embodiment will be described. Fig. 3 is a process diagram showing the steps of the energy conversion method according to this embodiment. As shown in Fig. 3, the energy conversion method according to this embodiment includes step S11 of preparing a fluctuation detection sensor having a nonlinear response layer, step S12 of inputting current fluctuations or heat flow fluctuations to the nonlinear response layer, and step S13 of converting the current fluctuations or heat flow fluctuations into energy. These steps will be described again with reference to Figs. 1 and 2.

[0032] In step S11 of preparing a fluctuation detection sensor having a nonlinear response layer, the above-mentioned fluctuation detection sensor 200 is prepared as shown in Figures 1 and 2. Subsequently, in step S12 of inputting current fluctuations or heat current fluctuations to the nonlinear response layer, current fluctuations J or heat current fluctuations H from the outside, which are the target of energy conversion, are input to the nonlinear response layer 202 in a state in which the ferromagnetic layer 203 has spontaneous magnetization 203M, so as to flow along the X-axis direction, which is one of the in-plane directions (in the XY plane) of the nonlinear response layer 202.

[0033] In this specification, "current fluctuation" refers to the phenomenon of current fluctuating over time and space, specifically, a situation in which a current in a certain direction (e.g., the X-axis direction) and a current in the opposite direction (e.g., the -X-axis direction) overlap each other, causing the direction of the net current to fluctuate over time and space. "Heat flow fluctuation" refers to the phenomenon of heat flow fluctuating over time and space, specifically, a situation in which a heat flow in a certain direction (e.g., the X-axis direction) and a heat flow in the opposite direction (e.g., the -X-axis direction) overlap each other, causing the direction of the net heat flow to fluctuate over time and space.

[0034] In step S12, when a current fluctuation J is input to the paramagnetic layer 205, a spin current J is generated by the spin Hall effect. S is generated along the Z-axis direction, and when the heat flow fluctuation H is input to the paramagnetic layer 205, the spin current J S is generated along the Z axis.

[0035] In step S13 of converting the energy of the current fluctuation or the heat current fluctuation, the spin current J generated as described above is converted into S flows into the ferromagnetic layer 203 in a state of having spontaneous magnetization 203M. S The polarity of changes to the positive or negative Y-axis direction depending on the direction of the current caused by the current fluctuation J (i.e., the net current direction of the current fluctuation J at a certain time and place) or the direction of the heat flow caused by the heat flow fluctuation H (i.e., the net heat flow direction of the heat flow fluctuation H at a certain time and place). Therefore, when the direction of the current or heat flow is reversed, the spin current J S The polarity of the spin current J S The relative orientation between the polarity of the magnetization 203M and the direction of the spontaneous magnetization 203M of the ferromagnetic layer 203 is reversed. In addition, by reversing the direction of the spontaneous magnetization 203M of the ferromagnetic layer 203, the spin current J S The relative orientation of the polarity of the magnetization 203M and the direction of the spontaneous magnetization 203M can also be reversed.

[0036] Spin current J S flows into the ferromagnetic layer 203, the spin current J S The electron scattering behavior changes depending on the relative orientation of the polarity of the spin current J and the spontaneous magnetization 203M of the ferromagnetic layer 203. S Since the polarity direction of changes depending on the direction of the electric current or heat flow, the mode of this electron scattering changes depending on the direction of the electric current or heat flow, which causes the voltage signal as the electric response signal generated in the nonlinear response layer 202 to depend on the direction of the electric current or heat flow, i.e., nonreciprocity.

[0037] In this way, the voltage conversion signal J as an electrical response signal generated in the nonlinear response layer 202 N is non-reciprocal with respect to the direction of the electric current or heat flow due to the non-reciprocal conduction of the non-linear response layer 202 as described above (i.e., the voltage conversion signal J N (changes in proportion to the quadratic of the current fluctuation J or heat flow fluctuation H), and regardless of whether the direction of the current or heat flow is the positive or negative X-axis direction, the voltage conversion signal J NThe direction of the non-reciprocal voltage conversion signal J is the positive direction of the X axis. N The inventors of the present application have found that the non-reciprocal voltage signal J can be electrically extracted via the pair of electrodes 207 a and 207 b. Therefore, according to the fluctuation detection sensor 200 of this embodiment, even if the direction or magnitude of the current caused by the current fluctuation J or the heat flow caused by the heat flow fluctuation H changes randomly, the non-reciprocal voltage signal J is generated in a fixed direction within the non-linear response layer 202. N Since it is possible to generate a current fluctuation J or a heat flow fluctuation H on a micro-scale, it becomes possible to detect energy fluctuations.

[0038] When a current fluctuation J is input to the nonlinear response layer 202, a nonreciprocal voltage signal J is extracted by the pair of electrodes 207a and 207b in the nonlinear response layer 202. N is the magnitude of the voltage V, the electric field generated in the nonlinear response layer 202 corresponding to V is E, the distance between the pair of electrodes 207a and 207b is L (D207 in FIG. 2), and the current density in the range of the distance L in the nonlinear response layer 202 is j, then electric field E = nonlinear electrical transport coefficient γ × electrical resistivity ρ × (current density j) 2 By multiplying both sides of this equation by the distance L, the voltage V = L × γ × ρ × j 2 Therefore, the greater the distance L between the pair of electrodes 207a and 207b, the greater the voltage V. Therefore, by setting the separation distance D207 between the pair of electrodes 207a and 207b in the X-axis direction to a large value, preferably 1000 μm or more, as described above, the non-reciprocal voltage signal J extracted by the pair of electrodes 207a and 207b can be reduced. N becomes larger.

[0039] Similarly, when a heat flow fluctuation H is input to the nonlinear response layer 202, a nonreciprocal voltage signal J is extracted by the pair of electrodes 207a and 207b in the nonlinear response layer 202. Nis the magnitude of the voltage V, the electric field generated in the nonlinear response layer 202 corresponding to V is E, the nonlinear Seebeck coefficient of the nonlinear response layer 202 is S, the distance between the pair of electrodes 207a and 207b is L (D207 in FIG. 2), the temperature gradient within the range of the distance L in the nonlinear response layer 202 is ∇T, and the temperature difference within the range of the distance L in the nonlinear response layer 202 is ΔT, then the electric field E = nonlinear Seebeck coefficient S × (temperature gradient ∇T) 2 By multiplying both sides of this equation by the distance L, we obtain the voltage V = nonlinear Seebeck coefficient S × (temperature difference ΔT) 2 / L, the smaller the distance L between the pair of electrodes 207a and 207b, the larger the voltage V. Therefore, by setting the separation distance D207 between the pair of electrodes 207a and 207b in the X-axis direction to a small value, preferably 1000 μm or less, as described above, the non-reciprocal voltage signal J extracted by the pair of electrodes 207a and 207b can be reduced. N becomes larger.

[0040] The fluctuation detection sensor 200 may also include a heat conducting portion provided in contact with or close to the end face on the positive side of the X-axis and / or the end face on the negative side of the X-axis, for facilitating the flow of the current fluctuation J or the heat current fluctuation H into the nonlinear response layer 202. Such a heat conducting portion may be made of, for example, aluminum, copper, carbon fiber, sapphire, alumina, silicon with a thermal oxide film, or a high molecular weight polymer.

[0041] 4 is a perspective view showing the configuration of a fluctuation detection sensor module using the fluctuation detection sensor described above. As shown in FIG. 4, a fluctuation detection sensor module 300 according to this embodiment includes a plurality of fluctuation detection sensors 200, and in this embodiment, has four fluctuation detection sensors 200a, 200b, 200c, and 200d. The four fluctuation detection sensors 200a, 200b, 200c, and 200d receive non-reciprocal voltage signals J from the respective nonlinear electron transport voltage conversion elements. N are electrically connected to each other so as to overlap with each other with the same polarity.

[0042] Specifically, in the fluctuation detection sensor module 300, fluctuation detection sensors 200a and 200c are arranged with respect to the Cartesian coordinate system C in a manner similar to the fluctuation detection sensor 200 shown in Figures 1 and 2, and fluctuation detection sensors 200b and 200d are arranged with respect to the Cartesian coordinate system C in a manner obtained by rotating the fluctuation detection sensor 200 shown in Figures 1 and 2 by 180 degrees around the Y axis, and are alternately provided along the Y axis. Then, electrode 207a of fluctuation detection sensor 200a is electrically connected to electrode 207b of fluctuation detection sensor 200b, electrode 207a of fluctuation detection sensor 200b is electrically connected to electrode 207b of fluctuation detection sensor 200c, and electrode 207a of fluctuation detection sensor 200c is electrically connected to electrode 207b of fluctuation detection sensor 200d. 1 and 2 with respect to the Cartesian coordinate system C, similar to fluctuation detection sensors 200a and 200c, but with the stacking order of the ferromagnetic layer 203 and the paramagnetic layer 205 of the nonlinear response layer 202 reversed in fluctuation detection sensors 200b and 200d. In this case, electrode 207a of fluctuation detection sensor 200a is electrically connected to electrode 207a of fluctuation detection sensor 200b, electrode 207b of fluctuation detection sensor 200b is electrically connected to electrode 207b of fluctuation detection sensor 200c, and electrode 207a of fluctuation detection sensor 200c is electrically connected to electrode 207a of fluctuation detection sensor 200d.

[0043] The fluctuation detection sensor module 300 also includes heat conduction units 301 and 302 that are provided in contact with or close to the end faces on the negative side and positive side of the X-axis of the four fluctuation detection sensors 200a, 200b, 200c, and 200d. This makes it easier for the heat flow in the X-axis direction to flow into the ferromagnetic layers 203 of each of the four fluctuation detection sensors 200a, 200b, 200c, and 200d. The fluctuation detection sensor module 300 does not necessarily have to include the heat conduction units 301 and 302.

[0044] The non-reciprocal voltage signals generated by the fluctuation detection sensors 200 when current fluctuations or heat flow fluctuations flow into the ferromagnetic layers 203 of the four fluctuation detection sensors 200a, 200b, 200c, and 200d are superimposed with the same polarity and then extracted by the electrode 207b of the fluctuation detection sensor 200a and the electrode 207a of the fluctuation detection sensor 200d, making it possible to extract a large non-reciprocal voltage signal. The fluctuation detection sensor module 300 can also be equipped with more fluctuation detection sensors 200, in which case it is possible to extract a larger non-reciprocal voltage signal.

[0045] (Example 1: Input of current fluctuation) Next, to clarify the effects of the present invention, examples will be described. In Example 1, an element corresponding to fluctuation detection sensor 200 was fabricated as follows, corresponding to step S11 of preparing a fluctuation detection sensor having a nonlinear response layer. First, a 0.5 mm-thick (111)-oriented magnesium oxide substrate was prepared as substrate 201. On this substrate, a ferromagnetic layer 203 was formed by co-sputtering Co at DC 37 W and Pt at RF 109 W at 0.046 nm / s using DC and RF magnetron sputtering methods, forming a 7.5 nm-thick CoPt alloy layer, which is an L10-type ordered alloy. Furthermore, a 7.5 nm-thick Pt layer was deposited on this CoPt alloy layer as paramagnetic layer 205, forming nonlinear response layer 202. Thereafter, by photolithography and lift-off, the nonlinear response layer 202 was patterned into a Hall element shape in plan view, that is, into a shape having a rectangular portion 10 μm wide in the Y-axis direction and 40 μm long in the X-axis direction in plan view, and two protrusions protruding in the Y-axis direction from each end of the rectangular portion. Thereafter, a Ti / Au layer was deposited on the nonlinear response layer 202 by RF magnetron sputtering, and the Ti / Au layer was patterned into a predetermined shape by photolithography and lift-off, thereby forming a pair of electrodes corresponding to the pair of electrodes 207 a, 207 b on the protrusions and a pair of electrodes 208 a, 208 b for an AC power supply 218 described below on both ends of the rectangular portion in the X-axis direction, thereby producing an element corresponding to the fluctuation detection sensor 200.

[0046] Next, for the element thus fabricated, experiments were carried out corresponding to step S12 of inputting current fluctuations or heat flow fluctuations to the nonlinear response layer and step S13 of converting the energy of the current fluctuations or heat flow fluctuations. Specifically, a current fluctuation was input to the element at room temperature (300K) in a manner corresponding to step S12, and a non-reciprocal voltage signal J was output from the pair of electrodes 207a and 207b. N Figure 5 shows the non-reciprocal voltage signal J N 5 is a schematic diagram showing an experimental method for measuring fluctuation. As shown in Fig. 5, an AC power supply 218 was electrically connected between a pair of electrodes 208a and 208b provided on fluctuation detection sensor 200. In addition, a lock-in amplifier 230 was electrically connected between a pair of electrodes 207a and 207b.

[0047] Then, while the magnitude of the external magnetic field B applied to the fluctuation detection sensor of Example 1 in the negative direction of the Y axis was changed from 2 T to -2 T, an AC current that changed sinusoidally with an angular frequency ω in the direction along the X axis was applied. Of the voltage signals generated by the fluctuation detection sensor of Example 1, ΔV 2ω、y was detected by a lock-in amplifier.

[0048] More specifically, when ω is the angular frequency and t is the time, the AC power supply 218 generates an AC current I AC =(√2)I rms An AC current expressed as sin(ωt) was applied (I rms means the effective value of AC current). I rms When the current is 0.01mA, I rmsExperiments were conducted for each of the cases where the current was 2.77 mA. A 6221-type AC / DC current source manufactured by Tektronix, Inc. in the United States was used as the AC power supply 218, and a lock-in amplifier LI5640 manufactured by NF Corporation was used as the lock-in amplifier 230. The frequency f (=ω / 2π) of the AC voltage applied by the AC power supply 218 was set to 13.423 Hz. The lock-in conditions for the lock-in amplifier 230 were a time constant of 1 second and a slope of -24 dB.

[0049] FIG. 6 shows the voltage signal ΔV obtained as a result of the above experiment in Example 1. 2ω、y 1 is a graph showing the dependence of I on an external magnetic field B. AC Since varies sinusoidally, the time average of the current flowing through the fluctuation detection sensor of Example 1 is zero (i.e., AC >=0), and I AC corresponds to the current fluctuation J on a micro-scale. If the voltage signal output from the fluctuation detection sensor of Example 1 is an AC current I AC If the polarity of the AC current I AC The voltage signal ΔV corresponding to twice the frequency of 2ω、y is the AC current I AC Since the voltage signals corresponding to the positive and negative phases of the AC current I cancel each other out, the voltage signal output from the fluctuation detection sensor in Example 1 becomes zero. AC If the voltage signal ΔV 2ω、y is a finite value.

[0050] In this experiment, as shown in Figure 6, rms is 2.77mA, when an external magnetic field B is applied, a finite value of ΔV 2ω、y is detected, and when the polarity of the external magnetic field B is reversed, ΔV 2ω、y As shown by the arrow in Figure 6, the polarity of the voltage signal ΔV 2ω、y has hysteresis, and the voltage signal ΔV 2ω、y ​It was revealed that the fluctuation detection sensor of Example 1 is capable of generating a voltage signal non-reciprocally relative to the direction of the current, and therefore it is possible to convert energy from the current fluctuation J to a non-reciprocal voltage signal even when the time average of the current is zero, even under conditions where an external magnetic field is not applied.

[0051] (Example 2: Input of heat flow fluctuation) Next, an experiment was conducted on Example 2. In Example 2, an element corresponding to fluctuation detection sensor 200 was fabricated as follows, corresponding to step S11 of preparing a fluctuation detection sensor having a nonlinear response layer. First, a 0.5 mm-thick (111)-oriented magnesium oxide substrate was prepared as substrate 201. On this substrate, a 7.5 nm-thick CoPt alloy layer, an L10-type ordered alloy, was co-sputter-deposited as ferromagnetic layer 203 using DC and RF magnetron sputtering. Co was deposited at DC 37 W and Pt was deposited at RF 109 W at 0.046 nm / s. Furthermore, a 5 nm-thick Pt layer was deposited on this CoPt alloy layer as paramagnetic layer 205 to form nonlinear response layer 202. Subsequently, photolithography and lift-off were used to pattern nonlinear response layer 202 into a rectangular shape in plan view, with a width of 7.5 μm in the Y-axis direction and a length of 60 μm in the X-axis direction. Thereafter, a Ti / Au layer was deposited on the nonlinear response layer 202 by RF magnetron sputtering, and the Ti / Au layer was patterned into a predetermined shape by photolithography and lift-off to form a pair of electrodes corresponding to the pair of electrodes 207a, 207b, thereby producing an element corresponding to the fluctuation detection sensor 200.

[0052] Next, for the element thus fabricated, experiments were carried out corresponding to step S12 of inputting current fluctuations or heat flow fluctuations to the nonlinear response layer and step S13 of converting the energy of the current fluctuations or heat flow fluctuations. Specifically, at room temperature (300 K), a heat flow fluctuation H was input to the element in step S12, and a non-reciprocal voltage signal J was output from the pair of electrodes 207a and 207b. NAn experiment was conducted to measure the fluctuation. As shown in Fig. 7, a first resistance heater 210 was provided adjacent to the end of an element corresponding to the fluctuation detection sensor 200 of Example 2 in the negative direction of the X-axis, and a second resistance heater 211 was provided adjacent to the end of the element in the positive direction of the X-axis. A first power supply 220 and a second power supply 221 were electrically connected to the first resistance heater 210 and the second resistance heater 211, respectively. A lock-in amplifier 230 was also electrically connected between the pair of electrodes 207a and 207b.

[0053] Then, while the magnitude of the external magnetic field B applied to the fluctuation detection sensor of Example 2 in the negative direction of the Y axis is changed from 2 T to −2 T, an AC temperature gradient ΔT that changes sinusoidally with an angular frequency ω in the direction along the X axis is generated by the first resistance heater 210 and the second resistance heater 211. AC Then, among the thermoelectric signals generated by the fluctuation detection sensor of Example 2, the AC temperature gradient ΔT AC ΔV is the y component of the change in the thermoelectric signal corresponding to twice the frequency of 2ω、y was detected by a lock-in amplifier.

[0054] AC temperature gradient ΔT AC More specifically, when ω is the angular frequency and t is the time, the first power supply 220 supplies V to the first resistance heater 210. dc +V ac sin(ωt) AC voltage is applied, and V dc -V ac An AC voltage of sin(ωt) was applied to the second resistance heater 211 by the second power supply 221. As a result, a change in the direction of the X-axis relative to the fluctuation detection sensor 200, ΔT AC =(√2)ΔT rms An AC temperature gradient expressed as sin(ωt) was applied (ΔT rmsis the effective value of the AC temperature gradient). A voltage source WF1948 manufactured by NF Corporation was used as the first power supply 220 and the second power supply 221, and a lock-in amplifier LI5640 manufactured by NF Corporation was used as the lock-in amplifier 230. The frequency f (=ω / 2π) of the AC voltages applied by the first power supply 220 and the second power supply 221 was set to 3.723 Hz. The lock-in conditions for the lock-in amplifier 230 were a time constant of 1 second and a slope of -24 dB.

[0055] FIG. 8 shows the voltage signal ΔV obtained as a result of the above experiment in Example 2. 2ω、y 10 is a graph showing the dependence of ΔT on the external magnetic field B. AC Since varies sinusoidally, when viewed on a macroscale, the fluctuation detection sensor of Example 2 is not substantially subjected to a temperature gradient, and ΔT AC corresponds to the temperature fluctuation on a micro scale. If the voltage signal output from the fluctuation detection sensor of Example 2 is AC If the polarity of the AC temperature gradient ΔT AC The voltage signal ΔV corresponding to twice the frequency of 2ω、y is the AC temperature gradient ΔT AC Since the thermoelectric signals corresponding to the positive and negative phases of the temperature gradient ΔT cancel each other out, the voltage signal output from the fluctuation detection sensor of Example 2 becomes zero. AC If the voltage signal ΔV 2ω、y is a finite value.

[0056] In this experiment, as shown in Figure 8, when an external magnetic field B is applied, a finite value of ΔV 2ω、y is detected, and when the polarity of the external magnetic field B is reversed, ΔV 2ω、y The polarity of the voltage signal ΔV 2ω、yIt was revealed that the fluctuation detection sensor of Example 2 is capable of generating a voltage signal non-reciprocally in the direction of the temperature gradient, and therefore it is possible to convert energy from heat flow fluctuations H at the microscale, where a temperature gradient does not substantially exist at the macroscale, into a non-reciprocal voltage signal.

[0057] The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0058] For example, in the above-described embodiment, the fluctuation detection sensor 200 includes the substrate 201 (see FIGS. 1 and 2), but the fluctuation detection sensor 200 does not necessarily have to include the substrate 201. In this case, the nonlinear response layer 202 can be formed as a free-standing layer.

[0059] Furthermore, in the above-described embodiment, in step S12 of inputting current fluctuations or heat flow fluctuations to the nonlinear response layer, either current fluctuations J or heat flow fluctuations H are input to the nonlinear response layer 202 (see Figures 1 and 2), but both current fluctuations J and heat flow fluctuations H may be input to the nonlinear response layer 202 in a superimposed manner.

[0060] Furthermore, in the above-described embodiment, step S12 of inputting current fluctuations or heat flow fluctuations into the nonlinear response layer and step S13 of converting the energy of the current fluctuations or heat flow fluctuations are performed when the ferromagnetic layer 203 has spontaneous magnetization 203M. However, these steps may also be performed while the ferromagnetic layer 203 is made of a soft magnetic material and an external magnetic field is applied to the ferromagnetic layer 203 to magnetize it to the same degree as the spontaneous magnetization 203M.

[0061] Furthermore, in the above-described embodiment, the pair of electrodes 207a, 207b are provided on the surface 205S of the paramagnetic layer 205 so as not to contact the ferromagnetic layer 203 and to be spaced apart from each other along the X-axis direction (see FIGS. 1 and 2). However, they may also be provided on the side surfaces of the paramagnetic layer 205 in the positive and negative X-axis directions so as not to contact the ferromagnetic layer 203 and to be spaced apart from each other along the X-axis direction.

[0062] Although the paramagnetic layer 205 in the above-described embodiment is a single layer (see FIGS. 1 and 2), the paramagnetic layer 205 may be composed of a plurality of stacked layers of paramagnetic metals. In this case, each of the plurality of layers is preferably composed of Pt, Pd, W, an AuW alloy, Ta, a CuIr alloy, a CuBi alloy, a BiSb alloy, or a BiSe alloy. Examples of such stacked layers of paramagnetic metals include a laminate in which layers of a plurality of types of paramagnetic metals are periodically stacked on top of each other (e.g., a laminate in which three types of layers are periodically stacked, such as Layer D, Layer E, Layer F, Layer D, Layer E, Layer F, etc., where Layer D is a layer of a first paramagnetic metal, Layer E is a layer of a second paramagnetic metal, and Layer F is a layer of a third paramagnetic metal), and a laminate in which layers of a plurality of types of paramagnetic metals are randomly stacked on top of each other (e.g., a laminate in which three types of layers are randomly stacked, such as Layer D, Layer E, Layer F, Layer E, Layer F, etc.). The stacked multiple paramagnetic metal layers preferably have spin Nernst angles of the same sign, because this prevents nonreciprocal voltage signals resulting from the multiple paramagnetic metal layers from canceling each other out during energy conversion in the nonlinear response layer 202, thereby increasing the overall nonreciprocal voltage signal.

[0063] Furthermore, in the above-described embodiment, the nonlinear response layer 202 includes only one paramagnetic layer (paramagnetic layer 205) such as a paramagnetic metal layer (see FIGS. 1 and 2 ). However, the nonlinear response layer 202 may include a first paramagnetic layer such as a paramagnetic metal layer and a second paramagnetic layer such as a paramagnetic metal layer. In this case, the nonlinear response layer 202 is configured by stacking the first paramagnetic layer, the ferromagnetic layer 203, and the second paramagnetic layer in this order along the Z-axis direction, with the ferromagnetic layer 203 interposed between the first and second paramagnetic layers. The preferred materials for the first and second paramagnetic layers are the same as those for the paramagnetic layer 205; however, it is preferable to select the configurations (materials, film thickness, etc.) of the first and second paramagnetic layers so that the nonlinear response layer 202 has a structure in which spatial inversion symmetry is broken along the Z-axis direction.

[0064] In this case, it is preferable that the first paramagnetic layer and the second paramagnetic layer have spin Nernst angles of opposite signs (for example, this can be achieved by configuring the first paramagnetic layer from Pt and the second paramagnetic layer from Ta). This is because, during energy conversion in the nonlinear response layer 202, spin currents of the same polarity are injected from the first paramagnetic layer and the second paramagnetic layer into the ferromagnetic layer 203, thereby increasing the nonreciprocal voltage signal.

[0065] Furthermore, in this case, either or both of the first and second paramagnetic layers may be composed of a plurality of paramagnetic metal layers stacked as described above. In this case, it is preferable that the plurality of paramagnetic metal layers constituting either or both of the first and second paramagnetic layers have spin-Nernst angles of the same sign for the reasons described above.

[0066] Furthermore, in the above-described embodiment, the pair of electrodes 207a, 207b are provided on the surface 205S of the paramagnetic layer 205 (see Figures 1 and 2), but the pair of electrodes 207a, 207b may also be provided on the back surface (the surface on the negative side of the Z-axis) of the ferromagnetic layer 203 so as not to be in contact with the paramagnetic layer 205 and to be spaced apart from each other along the X-axis direction.

[0067] In the above-described embodiment, the ferromagnetic layer 203 and the paramagnetic layer 205 are stacked in this order on the substrate 201 to form the nonlinear response layer 202 (see FIGS. 1 and 2), but the nonlinear response layer 202 may also be formed by stacking the paramagnetic layer 205 and the ferromagnetic layer 203 in this order on the substrate 201. In this case, the pair of electrodes 207a, 207b can be provided on the front surface of the ferromagnetic layer 203 (the surface on the positive side of the Z axis) or the back surface of the ferromagnetic layer 205 (the surface on the negative side of the Z axis) so as to be spaced apart from each other along the X-axis direction.

[0068] The fluctuation detection sensor of the present disclosure has the following configuration. [1] A nonlinear response unit having a nonlinear electrical response characteristic to an input of external energy along a first direction; an electrode unit for extracting an electrical response signal generated in the nonlinear response unit due to energy fluctuations input to the nonlinear response unit from the outside along the first direction; A fluctuation detection sensor equipped with [2] The fluctuation detection sensor according to [1], wherein the external energy is an electric current and / or a heat flow, and the energy fluctuation is an electric current fluctuation and / or a heat flow fluctuation. [3] The fluctuation detection sensor according to [1] or [2], wherein the external energy is an electric current and the energy fluctuation is a current fluctuation. [4] The fluctuation detection sensor according to any one of [1] to [3], wherein the nonlinear response section has a configuration in which spatial inversion symmetry is broken along a second direction perpendicular to the first direction. [5] The fluctuation detection sensor according to any one of [1] to [4], wherein the nonlinear response section includes a ferromagnetic layer and a paramagnetic layer stacked on top of each other along the second direction. [6] The fluctuation detection sensor according to any one of [1] to [5], wherein the ferromagnetic layer is configured to have spontaneous magnetization. [7] A fluctuation detection sensor according to any one of [1] to [6], wherein the ferromagnetic layer is a ferromagnetic metal layer and is made of an L10-type ordered alloy consisting of a magnetic metal and a paramagnetic metal, and the paramagnetic layer is a paramagnetic metal layer. [Explanation of symbols]

[0069] 200...fluctuation detection sensor, 202...nonlinear response layer, 207a, 207b...pair of electrodes (electrode portion).

Claims

1. a nonlinear response unit having a nonlinear electrical response characteristic to an input of external energy along a first direction; an electrode unit for extracting an electrical response signal generated in the nonlinear response unit due to energy fluctuations input to the nonlinear response unit from the outside along the first direction; A fluctuation detection sensor.

2. The fluctuation detection sensor according to claim 1 , wherein the external energy is an electric current and / or a heat flow, and the energy fluctuation is an electric current fluctuation and / or a heat flow fluctuation.

3. The fluctuation detection sensor according to claim 2 , wherein the external energy is a current, and the energy fluctuation is a current fluctuation.

4. The fluctuation detection sensor according to claim 1 , wherein the nonlinear response section has a configuration in which spatial inversion symmetry is broken along a second direction orthogonal to the first direction.

5. The fluctuation detection sensor according to claim 4 , wherein the nonlinear response unit includes a ferromagnetic layer and a paramagnetic layer stacked on top of each other along the second direction.

6. The fluctuation detection sensor according to claim 5 , wherein the ferromagnetic layer is configured to have spontaneous magnetization.

7. The ferromagnetic layer is a ferromagnetic metal layer, and the L1 layer is made of a magnetic metal and a paramagnetic metal. ０ 6. The fluctuation detection sensor according to claim 5, wherein the paramagnetic layer is made of an ordered alloy of the type, and the paramagnetic layer is a paramagnetic metal layer.

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