JP2022129848A - Magnetic material, laminate, and manufacturing method of laminate, thermoelectric conversion element, and magnetic sensor - Google Patents

Abstract

To provide a magnetic material that can be fabricated on a non-single-crystal substrate or a flexible substrate and has excellent thermoelectric conversion efficiency, a laminate, a manufacturing method of the laminate, and a thermoelectric conversion element and a magnetic sensor having the laminate.SOLUTION: A magnetic material has a polycrystalline Co-based Heusler alloy and having a film shape, and a crystal structure of the Co-based Heusler alloy is at least one selected from the group consisting of an L21 ordered structure and a B2 ordered structure, and the crystal orientation of the Co-based Heusler alloy is oriented in the thickness direction of the film.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetic material, a laminate, a method for manufacturing the laminate, a thermoelectric conversion element, and a magnetic sensor.

Patent Document 1 includes a thermoelectric conversion element made of an antiferromagnetic material having a non-collinear spin structure, and the thermoelectric conversion element has a temperature generated in a direction perpendicular to the in-plane minute magnetization direction due to the anomalous Nernst effect. A thermoelectric conversion device is described in which a voltage is generated due to the difference.

Patent Document 2 describes a thermoelectric conversion element that is made of a band-structured material having a Weyl point near the Fermi energy and has a thermoelectric mechanism that generates an electromotive force due to the anomalous Nernst effect.

Japanese Patent No. 6611167 WO2019/009308

However, the magnetic materials described in Patent Documents 1 and 2 are single crystal bulk samples or single crystal thin film samples. Therefore, there is a problem that it is difficult to fabricate a magnetic material on a non-single-crystal substrate or a flexible substrate. Moreover, when the magnetic material is not a single crystal, there is a problem that the thermoelectric conversion efficiency is not sufficient.

The present invention has been made in view of the above problems, and includes a magnetic material that can be produced on a non-single-crystal substrate or a flexible substrate and has excellent thermoelectric conversion efficiency, a laminate, a method for producing the laminate, and the laminate. An object of the present invention is to provide a thermoelectric conversion element and a magnetic sensor having the above.

In order to solve the above problems, the present invention provides the following means.
(1) One aspect of the magnetic material according to the present invention has a polycrystalline Co-based Heusler alloy and has a film shape,
The crystal structure of the Co-based Heusler alloy is at least _one selected from the group consisting of an L21 ordered structure and a B2 structure,
The crystal orientation of the Co-based Heusler alloy is oriented in the thickness direction of the film.
(2) The magnetic material described in (1) has a chemical composition represented by a composition formula of Co _α Mn _β X _γ ,
X is at least one selected from the group consisting of Ga, Al, Si and Ge;
α may range from 1.8 to 2.2, β may range from 0.8 to 1.2, and γ may range from 0.8 to 1.2.
(3) In the magnetic material described in (1) or (2), even if the half width of the X-ray diffraction peak of the crystal orientation of the Co-based Heusler alloy oriented in the thickness direction of the film is 1° or less good.
(4) In the magnetic material according to any one of (1) to (3), the thickness of the film may be 2 nm or more and 50 nm or less.
(5) One aspect of the laminate according to the present invention is a base material,
a buffer layer provided on the base material and containing AlN, wherein the crystal structure of AlN is at least one or more selected from the group consisting of cubic and hexagonal;
Provided on the buffer layer, from the side close to the buffer layer,
An alloy layer containing the magnetic material according to any one of claims 1 to 4;
The mixed layer includes AlN, and the AlN crystal structure includes a cap layer of at least one type selected from the group consisting of cubic crystals and hexagonal crystals.
(6) The laminate described in (5) may further have one or more mixed layers on the mixed layer.
(7) In the laminate described in (5) or (6), the buffer layer may have a thickness of 10 nm or more and 50 nm or less, and the cap layer may have a thickness of 1 nm or more and 50 nm or less.
(8) One aspect of the thermoelectric conversion element according to the present invention comprises a thermoelectric conversion material having the laminate according to any one of (5) to (7), and an electrode material. .
(9) One aspect of the magnetic sensor according to the present invention is characterized by having a detection portion that detects magnetism including the laminate according to any one of (5) to (7).
(10) One aspect of the method for producing a laminate according to the present invention is the method for producing a laminate according to any one of (5) to (7),
providing an AlN layer on the substrate;
providing an alloy layer having a Co-based Heusler alloy on the AlN layer;
providing a cap layer comprising AlN on the alloy layer;
and heat-treating the base material provided with the cap layer at 400° C. or higher and 800° C. or lower.
(11) In the method of manufacturing a laminate described in (10), in the heat treatment step, the pressure may be 10 ⁻⁴ Pa or less, and the heat treatment time may be 2 hours or more.

INDUSTRIAL APPLICABILITY According to the present invention, there are provided a magnetic material that can be produced on a non-single crystal substrate or a flexible substrate and has excellent thermoelectric conversion efficiency, a laminate, a method for producing the laminate, and a thermoelectric conversion element and a magnetic sensor having the laminate. can do.

It is a mimetic diagram of a layered product concerning an embodiment of the present invention. ₁ is a schematic diagram of the L21 ordered structure and electronic structure of a Co-based Heusler alloy; FIG. 1 is a schematic diagram of a thermoelectric conversion element according to an embodiment of the present invention; FIG. 1 is a schematic diagram showing a magnetic sensor according to an embodiment of the invention; FIG. It is a flow chart of a manufacturing method of a layered product concerning an embodiment of the present invention. 1 is a TEM photograph of a laminate according to an example of the present invention; It is the measurement result of the X-ray diffraction of the laminated body which concerns on the Example of this invention. It is the measurement result of the X-ray reflectance concerning the laminated body of the Example of this invention. It is a measurement result of the anomalous Nernst effect of the laminate according to the example of the present invention. 4 is a measurement result of the anomalous Hall effect of the laminate according to the example of the present invention; 4 is a TEM photograph of a laminate according to an example of the present invention; It is a figure which shows the measurement result of the abnormal Nernst voltage at the time of forming the magnetic material based on the Example of this invention on a flexible substrate. 4 is a photograph of a laminate in which a magnetic material according to an example of the present invention is formed on a polyimide substrate;

<Magnetic material>
First, a magnetic material according to an embodiment of the present invention will be described. A magnetic material according to an embodiment of the present invention comprises a Co-based Heusler alloy that is polycrystalline. The crystal structure of the Co-based Heusler alloy is at least _one selected from the group consisting of the L21 ordered structure and the B2 structure. A magnetic material according to an embodiment of the present invention is in the form of a film. The crystal orientation of the Co-based Heusler alloy is oriented in the thickness direction of the film. For example, the shape of the film is a thin film.

(Co-based Heusler alloy)
In this embodiment, the magnetic material comprises a Co-based Heusler alloy that is polycrystalline. The chemical composition of the Co-based Heusler alloy is preferably represented by a composition formula of Co _α Mn _β X _γ . However, X is at least one or more selected from the group consisting of Ga, Al, Si and Ge. Preferably, α is in the range of 1.8 to 2.2, β is in the range of 0.8 to 1.2, and γ is in the range of 0.8 to 1.2. This further improves the thermoelectric conversion efficiency of the magnetic material and the sensitivity of the magnetic sensor. Co-based Heusler alloys are polycrystalline. This improves the deformability of the magnetic material. The chemical composition of the magnetic material may be measured, for example, by energy dispersive X-ray spectroscopy (EDS). The deformability indicates the amount of macroscopic deformation of the membrane in the elastic region. Greater deformability indicates that greater deformation is allowed in the elastic range. Also, if the deformability is small, it indicates that the amount of deformation allowed in the elastic region is small.

(Crystal structure of Co-based Heusler alloy)
In this embodiment, the crystal structure of the Co-based Heusler alloy is at least _one selected from the group consisting of an L21 ordered structure and a B2 structure. This further improves the thermoelectric conversion efficiency of the magnetic material. FIG. 2 is a schematic diagram of the L21 ordered structure of _a Co-based Heusler alloy (source: Patent Document 2). As shown in FIG. 2, the L2 ₁ structure is a nested structure of four face-centered lattices. If the four sublattices are A, B, C, and D, the fractional coordinates are (0, 0, 0), (1/4, 1/4, 1/4), (1/2, 1/2), respectively. , 1/2), (3/4, 3/4, 3/4). In the L2 ₁ -ordered structure, U atoms occupy the A and C sites, V atoms occupy the B sites, and W atoms occupy the D sites. In FIG. 2, U atoms are Co, V atoms are Ga, and W atoms are Mn. In the L2 ₁ -ordered structure, the V atoms and W atoms may be completely interchanged. In the B2 structure, the arrangement of V and W atoms occupying the B and D sites is disordered. In the present embodiment, the crystal structure of the Co _- based Heusler alloy is more preferably an L21 ordered structure. This further improves the thermoelectric conversion efficiency of the magnetic material and the sensitivity of the magnetic sensor.

(membrane shape)
In this embodiment, the magnetic material is film-shaped. This improves the deformability of the magnetic material. The thickness of the film is preferably 2 nm or more and 50 nm or less. When the thickness of the film is 2 nm or more, the thermoelectric conversion efficiency of the magnetic material and the sensitivity of the magnetic sensor are further improved. The thickness of the film is preferably 5 nm or more, more preferably 8 nm or more, and even more preferably 10 nm or more. When the thickness of the film is 50 nm or less, the bending properties of the magnetic material are further improved. The thickness of the film is preferably 40 nm or less, more preferably 30 nm or less, and even more preferably 25 nm or less.

(Orientation of crystal orientation)
In this embodiment, the crystal orientation of the Co-based Heusler alloy is oriented in the thickness direction of the film. This improves the thermoelectric conversion efficiency of the magnetic material. The fact that the crystal orientation of the Co-based Heusler alloy is oriented in the thickness direction of the film means that the same crystal plane is observed when the magnetic material is viewed from a direction parallel to the thickness direction of the film. The half width of the X-ray diffraction peak of the crystal orientation of the Co-based Heusler alloy oriented in the thickness direction of the film is preferably 1° or less. As a result, the crystal orientation of the Co-based Heusler alloy is oriented higher in the thickness direction of the film. Moreover, the crystallinity of the Co-based Heusler alloy is further improved. As a result, the thermoelectric conversion efficiency of the magnetic material and the sensitivity of the magnetic sensor are further improved. The crystal orientation of the Co-based Heusler alloy oriented in the thickness direction of the film may be the (110) plane. Also, in this embodiment, since the magnetic material is polycrystalline, each crystal grain has a crystal grain obtained by rotating an arbitrary crystal grain around an axis in the thickness direction of the film.

Here, the half-value width of the X-ray diffraction peak is the half-value width of the X-ray diffraction peak obtained by measuring a plane perpendicular to the thickness direction of the film by an X-ray diffraction method. A known method can be used for the X-ray diffraction method.

The magnetic material according to this embodiment has the above configuration. Next, the effects of the magnetic material according to this embodiment will be described. A Co-based Heusler alloy exhibits a large anomalous Nernst effect (ANE) and an anomalous Hall effect (AHE). Therefore, it is attracting attention as a candidate material for high-sensitivity sensors and high-efficiency thermoelectric conversion elements.

One of the reasons why the Co-based Heusler alloy exhibits a large anomalous Nernst effect is that the topology of the electronic structure is characteristic. As shown in FIG. 3, in the vicinity of the Fermi energy EF, Co _{2 MnGa} has a linear dispersion in which a band forming the largest Fermi surface intersects with another band. The density of states (DOS) increases as the dispersion of both bands becomes nearly flat. Since Co _α Mn _β X _γ has a topological electronic structure as shown in FIG. 4, it is considered to exhibit a large anomalous Nernst effect.

The anomalous Nernst coefficient _SANE is considered to be represented by the following equation (1).
S _ANE =ρ _xx α _xy −S _SE ×tan θ _AHE (1)
where ρ _xx is the longitudinal resistivity, α _xy is the transverse thermoelectric conductivity, S _SE is the Seebeck coefficient, and θ _AHE is the anomalous Hall angle.

As shown in equation (1), the anomalous Nernst coefficient tends to increase as the anomalous Hall coefficient increases. Therefore, it is believed that materials with large anomalous Nernst coefficients often exhibit large anomalous Hall coefficients.

In order to develop the above excellent properties, a single crystal bulk material and a single crystal thin film grown on a single crystal substrate have been produced. However, bulk materials grown as single crystals and single-crystal thin films grown on single-crystal substrates have poor deformability, making it difficult to deform them into various shapes. Therefore, it has been difficult to apply the Co-based Heusler alloy to actual devices.

Since the magnetic material according to this embodiment is polycrystalline, it can be fabricated on a non-single-crystal substrate or a flexible substrate. Therefore, the magnetic material according to the present embodiment has high deformability compared to a bulk material grown as a single crystal and a single crystal thin film grown on a single crystal substrate. In addition, the magnetic material according to the present embodiment exhibits a large anomalous Nernst effect (ANE) and anomalous Hall effect (AHE) because the crystal orientation of the Co-based Heusler alloy is oriented in the thickness direction of the film. Therefore, the magnetic material according to this embodiment has high thermoelectric conversion efficiency and high magnetic sensitivity.

Next, a laminate 10 according to an embodiment of the present invention will be described with reference to the drawings. In addition, in the case of the same structure, the same code|symbol may be attached|subjected and description may be abbreviate|omitted.

<Laminate 10>
FIG. 1 shows a schematic diagram of a laminate 10 according to an embodiment of the invention. As shown in FIG. 1, the laminate 10 according to this embodiment has a base material 20, a buffer layer 30, a mixed layer 40a, and a mixed layer 40b. The mixed layer 40a has an alloy layer 41a and a cap layer 42a. The mixed layer 40b has an alloy layer 41b and a cap layer 42b.

A buffer layer 30 is provided on the substrate 20 . A mixed layer 40 a is provided on the buffer layer 30 . The mixed layer 40b is provided on the mixed layer 40a.

(Base material 20)
As shown in FIG. 1 , the base material 20 is a base portion of the laminate 10 . The base material 20 is made of a heat-resistant material. The substrate 20 preferably has heat resistance of 200° C. or higher. This further promotes the ordering of the Co _- based Heusler alloy layer to the L21 structure. The substrate 20 may be, for example, a heat-resistant inorganic material or an organic material. Substrates 20 include thermally oxidized Si, Al ₂ O ₃ , SiO ₂ , Glass and polyimide. The substrate 20 preferably has deformability. This further improves the deformability of the laminate. Although the thickness of the base material 20 is not particularly limited, the lower limit may be 50 nm or more, for example. Also, the upper limit may be, for example, 1 mm. If substrate 20 is a material having a crystalline structure, substrate 20 may be polycrystalline. The substrate may be a non-single crystal substrate or a flexible substrate.

(Buffer layer 30)
As shown in FIG. 1, buffer layer 30 is provided on substrate 20 . In this embodiment, buffer layer 30 comprises AlN. The crystal structure of AlN is at least one of the group consisting of cubic and hexagonal. Thereby, the orientation of the crystal orientation of the alloy layer 41a can be made appropriate. Also, the alloy layer 41a can be made to have a polycrystalline structure. Thereby, the deformability of the laminate 10 can be improved.

The buffer layer 30 can improve the crystallinity of the alloy layer 41a by being arranged between the base material 20 and the alloy layer 41a. As a result, crystal defects other than grain boundaries in the alloy layer 41a can be reduced. As a result, the thermoelectric conversion efficiency of the laminate 10 and the sensitivity of the magnetic sensor can be improved.

In this embodiment, the thickness of the buffer layer 30 is preferably 10 nm or more and 50 nm or less. When the buffer layer 30 has a thickness of 10 nm or more, the crystallinity of the alloy layer 41a can be further improved. Thereby, the thermoelectric conversion efficiency of the laminate 10 and the sensitivity of the magnetic sensor can be further improved. More preferably, the thickness of the buffer layer 30 is 18 nm or more. On the other hand, when the thickness of the buffer layer 30 is 50 nm or less, the thickness of the laminate 10 becomes small, and the bending deformability is further improved. More preferably, the thickness of the buffer layer 30 is 30 nm or less.

(Mixed layer 40a)
As shown in FIG. 1, the mixed layer 40a is provided on the buffer layer 30. As shown in FIG. The mixed layer 40a has an alloy layer 41a and a cap layer 42a from the side closer to the buffer layer. The alloy layer 41a comprises a magnetic material according to embodiments of the invention. Thereby, the deformability of the laminate 10 is improved. Also, the thermoelectric conversion efficiency of the laminate 10 and the sensitivity of the magnetic sensor are improved. The effect and preferred configuration of the alloy layer 41a are the same as those of the magnetic material according to the embodiment of the present invention.

In this embodiment, the cap layer 42a comprises AlN. The crystal structure of AlN is at least one of the group consisting of cubic and hexagonal. Thereby, the orientation of the crystal orientation of the alloy layer 41a and the alloy layer 41b can be made appropriate. Also, the alloy layer 41a and the alloy layer 41b can have a polycrystalline structure. Thereby, the deformability of the laminate 10 can be improved.

The cap layer 42a can improve the crystallinity of the alloy layer 41a and the alloy layer 41b by being arranged between the alloy layer 41a and the alloy layer 41b. As a result, crystal defects other than grain boundaries in the alloy layers 41a and 41b can be reduced. As a result, the thermoelectric conversion efficiency of the laminate 10 and the sensitivity of the magnetic sensor can be further improved.

The thickness of the cap layer 42a is preferably 1 nm or more and 50 nm or less. When the thickness of the cap layer 42a is 2 nm or more, the crystallinity of the alloy layers 41a and 41b can be further improved. Thereby, the thermoelectric conversion efficiency of the laminate 10 can be further improved. More preferably, the thickness of the cap layer 42a is 2 nm or more. On the other hand, when the thickness of the cap layer 42a is 5 nm or less, the deformability of the laminate 10 is further improved. More preferably, the thickness of the cap layer 42a is 5 nm or less.

(Mixed layer 40b)
As shown in FIG. 1, the mixed layer 40b is provided on the mixed layer 40a. The mixed layer 40b has an alloy layer 41b and a cap layer 42b from the side closer to the buffer layer. The alloy layer 41b has a magnetic material according to embodiments of the invention. The effect and preferred configuration of the alloy layer 41a are the same as those of the magnetic material according to the embodiment of the present invention. The effect and preferred configuration of the cap layer 42b are the same as those of the cap layer 42a.

The laminate 10 according to this embodiment has the above-described configuration. Next, the effects of the laminate 10 according to this embodiment will be described. The laminate 10 according to this embodiment is excellent in deformability because a base material with excellent deformability can be used. In addition, by sandwiching the alloy layer 41a and the alloy layer 41b with insulating AlN layers, the crystal orientation of the alloy layer 41a and the alloy layer 41b can be easily controlled and the crystallinity can be improved. be able to. As a result, the laminate 10 exhibits a large anomalous Nernst effect (ANE) and anomalous Hall effect (AHE). Therefore, the laminate 10 according to this embodiment has high thermoelectric conversion efficiency and high magnetic sensitivity.

The laminate 10 according to this embodiment may have three or more mixed layers. There may be a diffusion region between the alloy layer and the cap layer or buffer layer. The diffusion region has a composition intermediate between that of the alloy layer and that of the cap layer or buffer layer. Diffusion regions are preferably substantially absent.

<Thermoelectric conversion element>
Next, a thermoelectric conversion element 10a according to an embodiment of the present invention will be described with reference to the drawings. In addition, in the case of the same structure, the same code|symbol may be attached|subjected and description may be abbreviate|omitted.

FIG. 3 shows a schematic diagram of a thermoelectric conversion element 10a according to an embodiment of the present invention. As shown in FIG. 3, the thermoelectric conversion element 10a according to this embodiment has a thermoelectric conversion material 11 and an electrode material 12. As shown in FIG.

(Thermoelectric conversion material 11)
As shown in FIG. 3, the thermoelectric conversion material 11 is sheet-shaped. The thermoelectric conversion material 11 is spirally wound. The thermoelectric conversion material 11 has a cylindrical shape as a whole. A temperature gradient is generated in the axial direction of the cylinder, and an electromotive force is generated in the circumferential direction of the cylinder. Thereby, thermoelectric conversion is performed. In this embodiment, the thermoelectric conversion material 11 has a laminate according to the embodiment of the invention. Thereby, the thermoelectric conversion material 11 has great deformability and high thermoelectric conversion efficiency. The shape of the thermoelectric conversion material 11 is not particularly limited, and various shapes may be used according to the object or environment that produces a temperature gradient.

(Electrode material 12)
As shown in FIG. 3, the electrode material 12 is connected to both ends of the spirally wound thermoelectric conversion material 11 . Thereby, the electromotive force generated in the thermoelectric conversion material 11 can be used as current. The electrode material 12 may be any conductive material. An example of a conductive material is copper wire.

<Magnetic sensor>
Next, a magnetic sensor 10b according to an embodiment of the present invention will be described with reference to the drawings. In addition, in the case of the same structure, the same code|symbol may be attached|subjected and description may be abbreviate|omitted.

FIG. 4 is a schematic diagram showing a magnetic sensor 10b according to an embodiment of the invention. As shown in FIG. 4, the magnetic sensor 10b according to this embodiment has a detection unit 13. As shown in FIG.

(Detector 13)
The detection unit 13 detects a magnetic field. In this embodiment, the detection unit 13 has a laminate according to the embodiment of the invention. Thereby, the detection unit 13 has a large deformability and a high timing detection sensitivity.

<Method for manufacturing laminate>
Next, a method for manufacturing a laminate according to an embodiment of the present invention will be described. FIG. 5 shows a flowchart of a method for manufacturing a laminate according to this embodiment. As shown in FIG. 5, the method for manufacturing a laminate according to this embodiment has the following features.
(a) a step of providing an AlN layer on the substrate (b) a step of providing an alloy layer having a Co-based Heusler alloy on the AlN layer (c) a step of providing a cap layer having AlN on the alloy layer (d) ) A step of heat-treating the substrate provided with the cap layer at 400° C. or higher and 800° C. or lower

(Step of providing AlN layer on base material)
The step of providing the AlN layer on the substrate includes providing the AlN layer on the planar surface of the substrate. The method of providing the AlN layer on the substrate may be a vapor deposition method. Vapor deposition methods include a method of nitrogen reactive sputtering onto an Al target and a method of direct sputtering from an AlN target. In the case of nitrogen reactive sputtering onto an Al target, a mixed gas of Ar and _N2 may be used as the sputtering gas. In the case of direct sputtering from an AlN target, Ar gas may be used as the sputtering gas. The temperature of the substrate may be room temperature. The substrate may be thermally oxidized Si, Al ₂ O ₃ , SiO ₂ , Glass and polyimide. It is preferred to use substrates that are deformable. Moreover, it is preferable to use a substrate having heat resistance. The thickness of the substrate to be used is not particularly limited, but the lower limit may be, for example, 50 nm or more. Also, the upper limit may be, for example, 1 mm.

(Step of providing an alloy layer having a Co-based Heusler alloy on the AlN layer)
A method of providing an alloy layer having a Co-based Heusler alloy on the AlN layer may be a vapor deposition method. Vapor deposition methods include a vacuum deposition method and a sputtering method. The sputtering method may be DC sputtering from an alloy target or RF sputtering. The sputtering method may be co-sputtering from one or more sputter targets. The vacuum deposition method may be co-evaporation. In the sputtering method, inert gas ions generated by electric discharge collide with a target, which is a solid raw material, to eject elements of the raw material. The expelled raw material element deposits on the AlN layer. An alloy layer is thereby formed. In the vacuum deposition method, a Co-based Heusler alloy may be used as a raw material, or a simple metal may be used as a raw material.

(Step of providing a cap layer having AlN on the alloy layer)
In the step of providing a cap layer having AlN on the alloy layer, an AlN layer is provided on the alloy layer having the Co-based Heusler alloy. The method of providing the AlN layer on the alloy layer having the Co-based Heusler alloy may be a vapor deposition method. Vapor deposition methods include a method of nitrogen reactive sputtering onto an Al target and a method of direct sputtering from an AlN target. In the case of nitrogen reactive sputtering onto an Al target, a mixed gas of Ar and _N2 may be used as the sputtering gas. In the case of direct sputtering from an AlN target, Ar gas may be used as the sputtering gas. The method of providing the cap layer with AlN on the alloy layer may be the same as the method of providing the AlN layer on the substrate.

(Step of heat-treating the substrate provided with the cap layer at 400° C. or higher and 800° C. or lower)
A laminate obtained by providing a buffer layer, an alloy layer and a cap layer on a substrate is heat-treated at 400° C. or higher and 800° C. or lower. As a result, the Co-based Heusler alloy in the alloy layer becomes polycrystalline. Also, the crystal orientation of the Co-based Heusler alloy in the alloy layer is oriented in the thickness direction of the laminate. Furthermore, the crystal structure of the Co-based Heusler alloy in the alloy layer is at least one selected from the group consisting of the L21 _- ordered structure and the B2-ordered structure.

If the heat treatment temperature is less than 400° C., the crystal structure of the Co-based Heusler alloy in the alloy layer may not be at least _one of the group consisting of the L21 ordered structure and the B2 ordered structure. The heat treatment temperature is preferably 430° C. or higher, more preferably 480° C. or higher. On the other hand, if the heat treatment temperature exceeds 800° C., the crystal structure of the Co-based Heusler alloy in the alloy layer may not be at least _one of the group consisting of the L21 ordered structure and the B2 ordered structure. Also, the Co-based Heusler alloy in the alloy layer may not become polycrystalline. The heat treatment temperature is preferably 650° C. or lower, more preferably 550° C. or lower. Here, the heat treatment temperature refers to the temperature of the laminate.

The heat treatment pressure is not particularly limited as long as the crystal structure of the Co-based Heusler alloy in the alloy layer is at least _one selected from the group consisting of the L21 ordered structure and the B2 ordered structure. The heat treatment pressure may be 10 ⁻⁴ Pa or less. The heat treatment pressure is not particularly limited as long as the crystal structure of the Co-based Heusler alloy in the alloy layer is at least _one selected from the group consisting of the L21 ordered structure and the B2 ordered structure. The heat treatment pressure may be 2 hours or more.

When two or more alloy layers are provided in the laminate, the alloy layer and the cap layer may be further provided on the cap layer after performing the step of providing the cap layer containing AlN on the alloy layer. The method of providing the alloy layer and the cap layer can be the same as the method described above.

EXAMPLES Hereinafter, the effects of the present invention will be described more specifically with reference to examples. The conditions in the examples are an example of conditions adopted for confirming the feasibility and effect of the present invention, and the present invention is not limited to this example of conditions. Various conditions can be adopted in the present invention as long as the objects of the present invention are achieved without departing from the gist of the present invention.

In the examples, thermally oxidized Si was used as the substrate. First, a buffer layer of AlN was provided on the substrate by performing nitrogen reactive sputtering on an Al target. Al metal was used as the target, mixed gas of Ar and N ₂ was used as the atmosphere, and the film formation temperature was room temperature. Then, a Co ₂ MnGa (CMG) alloy layer was provided on the buffer layer by performing DC sputtering from an alloy target. The target was a Co ₂ MnGa alloy, the atmosphere was Ar gas, and the deposition temperature was room temperature. After that, an alloy layer and a cap layer were further provided. This resulted in a total of two mixed layers including the alloy layer and the cap layer. The obtained laminate was heat-treated under conditions of a heat treatment temperature of 500° C., a heat treatment time of 3 hours, and a heat treatment pressure of 10 ⁻⁴ Pa or less.

A plurality of laminates were produced by varying the thickness of the alloy layer. The thickness of the alloy layer of Example 1 was 2.5 nm. The thickness of the alloy layer of Example 2 was 5.0 nm. The thickness of the alloy layer of Example 3 was 12.5 nm. The thickness of the alloy layer of Example 4 was 25.0 nm. The thickness of the cap layer in Examples 1-4 was 5 nm. The thickness of the buffer layer in Examples 1-4 was 10 nm or more.

A cross section in the thickness direction and horizontal direction of the obtained laminate was observed with a transmission electron microscope (SEM). FIG. 6 shows a TEM photograph of a laminate according to an example of the present invention. As shown in FIG. 6, the laminate according to this example has a base material of thermally oxidized Si, a buffer layer of AlN, and a mixed layer having an alloy layer of Co ₂ MnGa and a cap layer of AlN. It has two layers in total. The interface of each layer had a sharp interface. No significant interdiffusion between layers was observed. It was also observed that the Co ₂ MnGa (CMG) alloy layer had polycrystallinity.

The crystal structure of each layer of the laminate was examined by X-ray diffraction (XRD). FIG. 7 shows the measurement results of X-ray diffraction of the laminate according to the example of the present invention. As shown in FIG. 7, a strong diffraction peak was observed on the (220) plane of CMG. That is, it was observed that the Co ₂ MnGa (CMG) alloy layer had a crystalline structure rather than being amorphous. It was also observed that the (110) plane of the Co ₂ MnGa (CMG) alloy was oriented perpendicular to the thickness direction of the laminate. Furthermore, Example 3 with an alloy layer thickness of 12.5 nm had the sharpest (220) plane diffraction peak.

As shown in FIG. 7, a strong diffraction peak was observed on the (002) plane of AlN. That is, in the AlN buffer layer and the cap layer, it was observed that the (001) plane of AlN was oriented perpendicular to the thickness direction of the laminate. Also, the AlN had a crystal orientation relationship in which the (001) plane was parallel to the (110) plane of the Co ₂ MnGa (CMG) alloy.

The surface roughness of the alloy layer of the obtained laminate was measured by X-ray reflectometry (XRR). FIG. 8 shows the measurement results of the X-ray reflectance of the laminate of the example of the present invention. For comparison, the measurement results obtained by the X-ray reflectance method before heat-treating the laminate are shown. As shown in FIG. 8, the surface roughness of the alloy layer of the laminate of the example of the present invention was Ra 0.31 nm. As a result, it was observed that the surface roughness of the alloy layer of the laminate of this example was low. Moreover, the surface roughness of the alloy layer before heat treatment of the laminate was Ra 0.85 nm. That is, it was observed that a firm laminated structure was formed by the heat treatment.

The anomalous Nernst effect of the obtained laminate was evaluated. As a method for measuring the anomalous Nernst effect, a magnetic field in the direction perpendicular to the plane of the laminate is swept while a temperature gradient is applied in the in-plane direction of the laminate. A method of measuring anomalous Nernst voltage was used. FIG. 9 shows measurement results of the anomalous Nernst effect of the laminate according to the example of the present invention. As shown in FIG. 9, in this example, an anomalous Nernst coefficient of 2.5 μV/K or more was measured. Also, an anomalous Nernst coefficient of 5 μV/K at maximum was measured. That is, it was found that the present example had high thermoelectric conversion efficiency.

The anomalous Hall effect of the resulting laminate was evaluated. As a method for measuring the anomalous Hall effect, a method was used in which a current was passed through the laminate, a magnetic field was applied in the direction perpendicular to the current, and the Hall electromotive force in the direction perpendicular to the current and the magnetic field was measured. FIG. 10 shows measurement results of the anomalous Hall effect of the laminate according to the example of the present invention. As shown in FIG. 10, the laminate according to this example exhibited a large anomalous Hall effect of 5% or more. Furthermore, a large anomalous Hall effect of up to 7.5% was exhibited. That is, this embodiment has high magnetic sensitivity.

A cross section parallel to the thickness of the obtained laminate was observed with a transmission electron microscope (TEM). FIG. 11 shows a TEM photograph of a laminate according to an example of the present invention. As shown in FIG. 11, it was observed that the crystal orientation of the Co ₂ MnGa (CMG) alloy layer was oriented in the thickness direction of the laminate. It was also observed that the Co ₂ MnGa (CMG) alloy layer was polycrystalline.

Therefore, since the laminate according to this example is polycrystalline, it has higher deformability than a single-crystal thin film. It also had a crystalline structure rather than the amorphous of the Co ₂ MnGa (CMG) alloy layer. As a result, the Co ₂ MnGa (CMG) alloy has a topological electronic band structure. Also, the crystal orientation of the Co ₂ MnGa (CMG) alloy layer was oriented in the thickness direction of the laminate. Therefore, the laminate according to this example exhibited a high anomalous Nernst coefficient and a high anomalous Hall angle. That is, it was confirmed that the laminate according to this example has high thermoelectric conversion efficiency and high magnetic sensitivity.

FIG. 12 shows measurement results of anomalous Nernst voltage when the magnetic material according to the example of the present invention is formed on a flexible substrate. As shown in FIG. 12, the magnetic material according to the embodiment of the present invention on the flexible substrate has a large anomalous Nernst coefficient of about 4 μV/K. A polyimide substrate was used as the flexible substrate.

FIG. 13 is a photograph of a laminate in which a magnetic material according to an example of the present invention is formed on a polyimide substrate. As shown in FIG. 13, laminates according to embodiments of the present invention have high flexibility.

Throughout the specification, when a part is referred to as "having" or "comprising" an element, this does not exclude other elements, unless specifically stated to the contrary. It means that it can contain more.

In addition, the terms "... part" and "... process" described in the specification mean a unit for processing at least one function or operation, which may be embodied as hardware or software, or may be implemented as hardware or software. It may be embodied in a combination of hardware and software.

In addition, it is possible to appropriately replace the constituent elements in the above-described embodiment with well-known constituent elements without departing from the spirit of the present invention, and the modifications described above may be combined as appropriate.

From the above, according to the present invention, a magnetic material that can be produced on a non-single-crystal substrate or a flexible substrate and has excellent thermoelectric conversion efficiency, a laminate, a method for producing a laminate, and a thermoelectric conversion element having the laminate and a magnetic sensor, the industrial utility value is high.

10 Laminate 10a Thermoelectric conversion element 10b Magnetic sensor 12 Electrode material 13 Detector 20 Base material 30 Buffer layers 40a, 40b Mixed layers 41a, 41b Alloy layers 42a, 42b Cap layer

Claims (11)

Having a polycrystalline Co-based Heusler alloy and having a film shape,
The crystal structure of the Co-based Heusler alloy is at least _one selected from the group consisting of an L21 ordered structure and a B2 structure,
A magnetic material, wherein the crystal orientation of the Co-based Heusler alloy is oriented in the thickness direction of the film. The chemical composition is represented by a compositional formula Co _α Mn _β X _γ ,
X is at least one selected from the group consisting of Ga, Al, Si and Ge;
α is in the range of 1.8 to 2.2, β is in the range of 0.8 to 1.2, and γ is in the range of 0.8 to 1.2. The magnetic material described in . 3. The magnetic material according to claim 1, wherein the half width of the X-ray diffraction peak of the crystal orientation of the Co-based Heusler alloy oriented in the thickness direction of the film is 1[deg.] or less. 4. The magnetic material according to claim 1, wherein the film has a thickness of 2 nm or more and 50 nm or less. a substrate;
a buffer layer provided on the base material and containing AlN, wherein the crystal structure of AlN is at least one or more selected from the group consisting of cubic and hexagonal;
Provided on the buffer layer, from the side close to the buffer layer,
An alloy layer containing the magnetic material according to any one of claims 1 to 4;
A mixed layer comprising AlN and a cap layer in which the crystal structure of AlN is at least one selected from the group consisting of cubic and hexagonal crystals. 6. The laminate according to claim 5, further comprising one or more layers of the mixed layer on the mixed layer. 7. The laminate according to claim 5, wherein the buffer layer has a thickness of 10 nm or more and 50 nm or less, and the cap layer has a thickness of 1 nm or more and 50 nm or less. A thermoelectric conversion element comprising: a thermoelectric conversion material having the laminate according to any one of claims 5 to 7; and an electrode material. A magnetic sensor comprising a detection unit that detects magnetism including the laminate according to any one of claims 5 to 7. A method for producing a laminate according to any one of claims 5 to 7,
providing an AlN layer on the substrate;
providing an alloy layer having a Co-based Heusler alloy on the AlN layer;
providing a cap layer comprising AlN on the alloy layer;
and heat-treating the substrate provided with the cap layer at a temperature of 400° C. or higher and 800° C. or lower. 11. The method for producing a laminate according to claim 10, wherein in the heat treatment step, the pressure is 10 ⁻⁴ Pa or less and the heat treatment time is 2 hours or more.

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