Compound, magnetic material, module, heat source, and magnetic refrigeration device

Abstract

To provide a compound, a magnetic material, a module, a heat source, and a magnetic refrigeration device that exhibit large magnetic entropy changes.SOLUTION: The compound includes four or more elements in a Heusler structure in which a structural first-order phase transition and a magnetic second-order phase transition occur successively. The magnetic material includes a first compound and a second compound. The heat source includes the magnetic material and an application part that applies a magnetic field to the magnetic material. The magnetic refrigeration device includes the heat source and a moving part that moves a fluid that performs heat exchange with the magnetic material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a compound, a magnetic material, a module, a heat source, and a magnetic refrigeration device. [Background technology]

[0002] Conventionally, as an environmentally friendly refrigeration technology, magnetic refrigeration using magnetic entropy change has been researched and developed. For example, Patent Document 1 (JP Patent Publication 2008-150695 A) is an example of a magnetic material used in such magnetic refrigeration. Patent Document 1 describes NaZn2+, which contains 4 atomic % to 15 atomic % of La, 3 atomic % to 25 atomic % of Si, 1.5 atomic % to 10 atomic % of Co, and 50 atomic % to 91.5 atomic % of Fe. 13 A magnetic refrigeration material is disclosed, which is an alloy having a crystal structure of the above type in the main phase, and is characterized in that the alloy contains 0.29 atomic % or more and 2.8 atomic % or less of C. Summary of the Invention [Problem to be solved by the invention]

[0003] As described in the above-mentioned patent document, materials that exhibit large magnetic entropy changes are desirable. [Means for solving the problem]

[0004] The compound according to the first aspect contains four or more elements in a Heusler structure, and a first-order structural phase transition and a second-order magnetic phase transition occur successively.

[0005] According to the compound of the first aspect, since the Heusler structure contains four or more elements, it is possible to increase the amount of entropy change accompanying the magnetic second-order phase transition. Furthermore, since the structural first-order phase transition occurs successively to the magnetic second-order phase transition, it is possible to increase the amount of entropy change accompanying the first-order phase transition. Therefore, the compound of the first aspect can show a large magnetic entropy change.

[0006] The compound according to the second aspect includes all of the elements chromium (Cr), cobalt (Co), iron (Fe) and phosphorus (P) in the compound according to the first aspect.

[0007] In the compound of the second aspect, by including Cr, Co, Fe and P as the four or more elements, it is possible to easily realize a large magnetic entropy change.

[0008] The compound according to the third aspect is the compound according to the second aspect, further comprising a fifth element.

[0009] Like the compounds of the third aspect, compounds of the present disclosure may contain five or more elements.

[0010] A magnetic material according to a fourth aspect includes a first compound and a second compound. The first compound is a compound according to any one of the first aspect to the third aspect. The second compound has a different composition from the first compound.

[0011] Like the magnetic material of the fourth aspect, it may contain two or more compounds.

[0012] A magnetic material according to a fifth aspect is the magnetic material according to the fourth aspect, in which the second-order phase transition temperature of the first compound is different from the second-order phase transition temperature of the second compound.

[0013] In the magnetic material of the fifth aspect, by using compounds having different phase transition temperatures, heat exchange using the magnetic material can be efficiently carried out.

[0014] The module according to the sixth aspect links a first compound according to the fourth or fifth aspect to a second compound according to the fourth or fifth aspect.

[0015] In the magnetic material of the sixth aspect, the fluid that has been heat exchanged by one of the first compound and the second compound can be further heat exchanged by the other of the first compound and the second compound.

[0016] A heat source according to a seventh aspect includes a magnetic material and an application unit. The magnetic material is the magnetic material according to the fourth or fifth aspect. The application unit applies a magnetic field to the magnetic material.

[0017] In the heat source of the seventh aspect, heat exchange with the fluid can be performed by utilizing heat released from the magnetic material to which a magnetic field is applied from the application unit.

[0018] A magnetic refrigeration apparatus according to an eighth aspect includes a heat source and a moving unit. The heat source is the heat source according to the seventh aspect. The moving unit moves a fluid that exchanges heat with the magnetic material.

[0019] In the magnetic refrigeration device of the eighth aspect, a fluid that has been heated by heat exchange with a magnetic material can be moved by a moving unit to extract hot heat, and a fluid that has absorbed heat by heat exchange with a magnetic material can be moved by a moving unit to extract cold heat. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a diagram showing an image in which a first-order phase transition and a second-order phase transition occur successively in a compound according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is an external configuration diagram of a module according to an embodiment of the present disclosure. [Diagram 3] FIG. 13 is an external configuration diagram of a module according to another embodiment of the present disclosure. [Figure 4] FIG. 2 is a schematic diagram of a heat source according to an embodiment of the present disclosure. [Diagram 5] 1 is a schematic configuration diagram of a magnetic refrigeration device according to an embodiment of the present disclosure. [Figure 6] 1 is a graph showing the temperature of the second-order phase transition and the performance index of a Heusler compound. [Figure 7] 7 is a graph showing the temperature and entropy change of the second-order phase transition of the Heusler compound extracted from FIG. 6. [Figure 8] 1 is a graph showing the entropy change with respect to temperature of a compound including four elements, Cr, Co, Fe, and P, in a Heusler structure. [Figure 9] 1 is a graph showing the entropy change with respect to temperature for La(Fe0.85Si0.15)13. [Figure 10] 1 is a graph showing the temperature and lattice size of a second-order phase transition of a compound including four elements, Cr, Co, Fe, and P, in a Heusler structure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, a compound, a magnetic material, a module, and a magnetic refrigeration device according to an embodiment of the present disclosure will be described with reference to examples.

[0022] (1) Compound (1-1) Overview The compound of the present embodiment includes four or more elements in the Heusler structure, which is different from the conventional Heusler compound consisting of three elements, and therefore the compound of the present embodiment includes four or more elements in the Heusler structure, which may enhance the magnetocaloric effect.

[0023] The four or more elements are, for example, selected from Cr, Co, Fe, P, metal elements of the second period, the third period, and the fourth period, and nonmetallic elements, and in this case, it is preferable to include all of the elements Cr, Co, Fe, and P. When the compound is composed of Cr, Co, Fe, and P, the composition ratio of Cr, Co, Fe, and P is more preferably Cr:Co:Fe:P=(0.5-1.5):(0.5-1.5):(0.5-1.5):(0.5-1.5).

[0024] The compound may contain five or more elements. In this case, the compound preferably contains Cr, Co, Fe, P, and a fifth element. Examples of the fifth element include, but are not limited to, silicon (Si), aluminum (Al), germanium (Ge), tin (Sn), and hydrogen (H). In this case, when the composition ratio of Cr, Co, Fe, P, and the fifth element is expressed as Cr:Co:Fe:P:fifth element, the composition ratio of the fifth element is smaller than the composition ratios of the other four elements.

[0025] The fifth element may be introduced, for example, between the crystal lattice or may substitute for some of the lattice sites.

[0026] In addition, compounds undergo a first-order structural phase transition and a second-order magnetic phase transition successively. A first-order phase transition is a transformation in which the crystal structure changes, such as a martensitic transformation. A first-order phase transition occurs when the temperature drops to the martensitic transformation temperature. A second-order phase transition is a magnetic phase transition, such as a phenomenon in which a paramagnetic material changes to a ferromagnetic material. A second-order phase transition occurs at the Curie temperature.

[0027] Here, in a compound, the temperature at which a first-order phase transition occurs (hereinafter also referred to as the "temperature of the first-order phase transition") and the temperature at which a second-order phase transition occurs (hereinafter also referred to as the "temperature of the second-order phase transition") are substantially the same. "Substantially the same" means that the temperature difference is within about 2 K. It is to be noted that either the first-order phase transition or the second-order phase transition may occur first.

[0028] The temperature of the first-order phase transition and the temperature of the second-order phase transition can be set according to the application of the object of heat exchange, and is preferably, for example, 270K or more and 310K or less.

[0029] FIG. 1 shows an image of a compound in which a first-order phase transition and a second-order phase transition occur successively. In FIG. 1, the horizontal axis indicates temperature, and the vertical axis indicates energy in the compound. Here, the energy in the compound is entropy. Also, Tc is the temperature at which a first-order phase transition occurs, and the temperature at which a second-order phase transition occurs. As shown in FIG. 1, when the temperature of the compound drops from the temperature Ta of point A to the temperature Tc of point B, a magnetic second-order phase transition occurs, and energy is released up to point C. Then, a structural first-order phase transition occurs from point C, and energy is released up to point D. Thus, when the compound of this embodiment reaches the temperature Tc, a first-order phase transition and a second-order phase transition occur successively, and energy is released from point B to point D. Here, the compound has a martensitic transformation temperature, which is the temperature of a first-order phase transition, in the vicinity of the Curie temperature, which is the temperature of a second-order phase transition, and therefore a first-order phase transition accompanying the martensitic transformation occurs together with a magnetic second-order phase transition, and thus shows a large entropy change.

[0030] Such compounds constitute magnetic materials and are used in magnetic refrigeration devices that use the active magnetic refrigeration (AMR) method.

[0031] (1-2) Manufacturing method The compound of this embodiment is produced by selecting four or more elements that cause a first-order structural phase transition and a second-order magnetic phase transition to occur successively, and introducing the selected four or more elements into a Heusler structure.

[0032] Moreover, after the four elements are introduced into the Heusler structure, a part of them may be replaced with a fifth element.

[0033] The temperature of the second-order phase transition can be controlled by adjusting the lattice size, and therefore, the lattice size is further selected such that the temperature of the second-order phase transition is substantially the same as the temperature of the first-order phase transition for the four or more selected elements.

[0034] (2)Magnetic material (2-1) Overview The magnetic material includes a first compound and a second compound. The second compound has a different composition from the first compound. The first compound is the compound (1) above. The second compound does not have to be the compound (1) above, but in this embodiment, it is the compound (1) above. It is preferable that the Curie temperature, which is the temperature of the second-order phase transition of the first compound, is different from the Curie temperature, which is the temperature of the second-order phase transition of the second compound. The second-order phase transition temperature of the first compound may be higher or lower than the second-order phase transition temperature of the second compound.

[0035] The magnetic material, for example, obtains a magnetocaloric effect by changing the entropy in the first compound and the second compound, and exchanges heat with the fluid. In other words, the magnetic material can be used to cool or heat the fluid. The first compound and the second compound generate heat when a magnetic field is applied, and absorb heat when the application of the magnetic field is stopped and the magnetic field is removed.

[0036] The magnetic material is not limited as long as it contains at least two types of compounds.

[0037] (2-2) Method for identifying compounds in magnetic materials To identify compounds in magnetic materials, the crystalline phase can be identified by measuring the interstitial distance using XRD (X-ray Diffraction).

[0038] Moreover, by observing the backscattered electron image of the surface of a compound using SEM (Scanning Electron Microscopy), it is possible to distinguish between areas with different crystal phases.

[0039] Furthermore, the distribution of elements on a surface or cross section can be analyzed by methods using electron beams, such as EPMA (Electron Probe Micro Analyzer) or EDX (Energy dispersive X-ray spectroscopy).

[0040] (3) Module (3-1) Overview The module is arranged with at least two kinds of compounds side by side. The shape and arrangement of the module are not particularly limited. The first compound and the second compound constituting the module are preferably arranged side by side, more preferably arranged in thermal contact with each other, and more preferably arranged in direct physical contact with each other. This makes it possible to increase the efficiency when used as an AMR module.

[0041] 2, in the module 10 of the present embodiment, a first compound 11 and a second compound 12 are linked together. Specifically, the module 10 has a first compound 11 having a streak-like recessed portion on its upper portion, and a second compound 12 similarly having a streak-like recessed portion on its upper portion, and the first compound 11 and the second compound 12 are arranged so that the recessed portions are continuous with each other.

[0042] In addition, the module 10 may have three or more compounds arranged in parallel or in parallel with each other as shown in Fig. 3. Also, three or more compounds may be arranged so as to overlap each other in the vertical direction.

[0043] (3-2) Manufacturing method An example of a method for manufacturing the module 10 shown in FIG. 2 will be described. First, the first compound and the second compound are manufactured as described above in (1-2). Next, the first compound and the second compound are placed in a mold with a partition, respectively, and then the partition is removed and pressed. This makes it possible to manufacture the module 10 in which the first compound 11 and the second compound 12 are connected.

[0044] (4)Heat source The heat source of this embodiment exchanges heat with a fluid by utilizing heat released from a magnetic material. The heat source includes the magnetic material and the application unit described above in (2). Here, the heat source includes the module and the application unit described above in (3).

[0045] The application unit applies a magnetic field to the magnetic material. In particular, the application unit can change the magnetic field applied to the magnetic material. The application unit has a magnetic circuit and the like, and has a portion located on one side and a portion located on the other side of the magnetic material including the first compound and the second compound.

[0046] The application unit can switch between a state in which a magnetic field is applied to the magnetic material and a state in which a magnetic field is not applied. The application unit may also be capable of performing a process of strengthening the magnetic field on the magnetic material and a process of weakening the magnetic field without reducing it to zero.

[0047] Such a heat source can be configured, for example, as a heat source 1 shown in Fig. 4. This heat source 1 includes a module 10 made of a magnetic material, and an application unit 30.

[0048] The first compound 11 and the second compound 12 constituting the module 10 (magnetic material) are provided, for example, so as to be in contact with each other. The application unit 30 has a portion located on one side of the module 10 and a portion located on the other side, and can apply a magnetic field to the module 10, and can also stop the application of the magnetic field to remove the magnetic field.

[0049] (5) Magnetic refrigeration equipment The magnetic refrigeration device of this embodiment is of the AMR type, and includes the heat source (4) and a moving unit.

[0050] The moving part moves a fluid that exchanges heat with the magnetic material. The fluid is in thermal contact with the magnetic material. The fluid is, for example, a heat medium such as a refrigerant or water.

[0051] In detail, the moving part moves the fluid relative to the magnetic material included in the module. The moving part is not particularly limited, and may be composed of pistons provided on both sides of the magnetic material, or may be composed of a pump provided in a closed circuit.

[0052] Such a magnetic refrigeration device can be configured, for example, as a magnetic refrigeration device 100 shown in Fig. 5. The magnetic refrigeration device 100 here is a temperature control device. The magnetic refrigeration device 100 includes a heat source 1, a movement circuit 60, a high-temperature side circuit 40, and a low-temperature side circuit 50.

[0053] As described above, the heat source 1 has a module 10 made of a magnetic material and an application unit 30. The magnetic material constituting the module 10 in FIG. 5 has, for example, a first compound 11, a second compound 12, a third compound 13, and a fourth compound 14. Here, the first compound 11, the second compound 12, the third compound 13, and the fourth compound 14 are the compounds (1) above, and have different compositions. The first compound 11, the second compound 12, the third compound 13, and the fourth compound 14 are composed of compounds having higher secondary phase transition temperatures in this order. The first compound 11, the second compound 12, the third compound 13, and the fourth compound 14 are arranged in order of higher secondary phase transition temperatures. The application unit 30 can apply a magnetic field to all of the first compound 11, the second compound 12, the third compound 13, and the fourth compound 14 contained in the magnetic material (module 10), and can remove the magnetic field by weakening or stopping the applied magnetic field.

[0054] The movement circuit 60 has a tank 62, a pump 63, and a flow path 61 connecting them, and a fluid is sealed inside. The magnetic material constituting the module 10 may be disposed inside the tank 62, or may be disposed outside the tank 62 so that the fluid inside the tank 62 and the magnetic material are thermally in contact with each other. The tank 62 has a high-temperature storage section 62a that is a high-temperature side with respect to the module 10, and a low-temperature storage section 62b that is a low-temperature side with respect to the module 10. In the module 10, a compound having a high secondary phase transition temperature is located on the high-temperature storage section 62a side, and a compound having a low secondary phase transition temperature is located on the low-temperature storage section 62b side. When a magnetic field is applied from the application section 30 to the module 10 and the fluid is heated by the heat radiated from the module 10, the pump 63 is driven to move the fluid to the high-temperature side with respect to the module 10. As a result, the high-temperature fluid is stored in the high-temperature storage section 62a. Furthermore, when the application unit 30 stops applying the magnetic field to the module 10 and removes the magnetic field, the module 10 absorbs heat from the fluid, and when the temperature of the fluid drops, the pump 63 is driven to move the fluid to the low temperature side of the module 10. As a result, the low temperature fluid is stored in the low temperature storage unit 62b. By repeating the above-mentioned movement of the fluid and the application and removal of the magnetic field, the high temperature fluid is collected in the high temperature storage unit 62a, and the low temperature fluid is collected in the low temperature storage unit 62b.

[0055] The high-temperature side circuit 40 has a high-temperature side first heat exchanger 41, a high-temperature side pump 44, a high-temperature side second heat exchanger 42, and a high-temperature side flow path 43 connecting them, and a high-temperature side heat medium such as a refrigerant or water circulates inside. The high-temperature side first heat exchanger 41 is provided in the high-temperature storage section 62a, and heat exchange is performed between the high-temperature side heat medium flowing inside the high-temperature side first heat exchanger 41 and the high-temperature fluid in the high-temperature storage section 62a. The high-temperature side second heat exchanger 42 uses the high temperature of the high-temperature side heat medium flowing inside to heat an object to be temperature-adjusted. The object to be temperature-adjusted may be air, a fluid such as water, or a solid to be heated. The high-temperature side flow path 43 connects the high-temperature side first heat exchanger 41, the high-temperature side pump 44, and the high-temperature side second heat exchanger 42 so that the high-temperature side heat medium can circulate between them. The high-temperature side pump 44 circulates the high-temperature side heat medium within the high-temperature side circuit 40 when driven.

[0056] The low-temperature side circuit 50 has a low-temperature side first heat exchanger 51, a low-temperature side pump 54, a low-temperature side second heat exchanger 52, and a low-temperature side flow path 53 connecting them, and a low-temperature side heat medium such as a refrigerant or water circulates inside. The low-temperature side first heat exchanger 51 is provided in the low-temperature storage section 62b, and heat exchange is performed between the low-temperature side heat medium flowing inside the low-temperature side first heat exchanger 51 and the low-temperature fluid in the low-temperature storage section 62b. The low-temperature side second heat exchanger 52 cools a temperature adjustment target by utilizing the low temperature of the low-temperature side heat medium flowing inside. The temperature adjustment target may be air, a fluid such as water, or a solid to be cooled. The low-temperature side flow path 53 connects the low-temperature side first heat exchanger 51, the low-temperature side pump 54, and the low-temperature side second heat exchanger 52 so that the low-temperature side heat medium can circulate between them. The low-temperature side pump 54 circulates the low-temperature side heat medium within the low-temperature side circuit 50 when driven.

[0057] (6) Features (6-1) Compounds 11 and 12 according to this embodiment contain four or more elements in a Heusler structure, and a first-order structural phase transition and a second-order magnetic phase transition occur successively.

[0058] According to compounds 11 and 12 of the present embodiment, since the Heusler structure contains four or more elements, the amount of entropy change accompanying the magnetic second-order phase transition can be increased. Furthermore, since the structural first-order phase transition occurs successively to the magnetic second-order phase transition, the amount of entropy change accompanying the first-order phase transition can be increased. Therefore, compounds 11 and 12 of the present embodiment have a higher entropy change than conventional NaZn 13 Compared to materials with this structure (La-Fe-Si based materials), it can exhibit a large magnetic entropy change.

[0059] In addition, since the compounds 11 and 12 of the present embodiment exhibit a large magnetic entropy without the application of pressure other than the magnetic field, a pressure generating device can be omitted, and thus the device including the compounds 11 and 12 can be made smaller and lighter.

[0060] In addition, the compounds 11 and 12 of the present embodiment exhibit a large magnetocaloric effect at around room temperature, so that they can be cooled or heated at around room temperature. Therefore, the compounds 11 and 12 of the present embodiment can be suitably used in refrigerators, heating devices, cooling devices, etc., and are suitably used in air conditioning devices that replace vapor compression types.

[0061] (6-2) Compounds 11 and 12 according to this embodiment contain all of the elements Cr, Co, Fe and P in the compound according to (6-1) above.

[0062] Here, by including Cr, Co, Fe and P as the four or more elements, it is possible to easily realize a large magnetic entropy change.

[0063] (6-3) Compounds 11 and 12 according to this embodiment further contain a fifth element in the compound according to (6-2) above.

[0064] Thus, compounds 11 and 12 may contain five or more elements. The compound containing five elements is preferably a Heusler compound in which a fifth element is introduced between the lattices to adjust the lattice size and change the temperature of the second-order phase transition, or a Heusler compound in which a part of the lattice sites is substituted with the fifth element to adjust the lattice size and change the temperature of the second-order phase transition.

[0065] (6-4) The magnetic material according to this embodiment includes a first compound 11 and a second compound 12. The first compound 11 is a compound according to any one of the above (6-1) to (6-3). The second compound 12 has a different composition from the first compound 11.

[0066] In this way, the magnetic material may contain two or more kinds of compounds 11 and 12. The second compound 12 may be any of the compounds according to (6-1) to (6-3) above, or may not be any of the compounds according to (6-1) to (6-3) above.

[0067] (6-5) In the magnetic material according to this embodiment, the first compound 11 and the second compound 12 in the magnetic material according to (6-4) above have different second-order phase transition temperatures.

[0068] Here, by using compounds 11 and 12 having different phase transition temperatures, heat exchange with a fluid using a magnetic material can be efficiently performed.

[0069] (6-6) In the module 10 according to this embodiment, the first compound 11 and the second compound 12 are linked together in the magnetic material according to (6-4) or (6-5) above.

[0070] Here, the fluid that has been heat exchanged by one of the first compound 11 and the second compound 12 can be further heat exchanged by the other of the first compound 11 and the second compound 12.

[0071] (6-7) The heat source 1 according to this embodiment includes a magnetic material (a module 10 in this embodiment) and an application unit 30. The magnetic material is the magnetic material according to either (6-4) or (6-5) above. The application unit 30 applies a magnetic field to the magnetic material.

[0072] Here, heat exchange with the fluid can be performed by utilizing heat released from the magnetic material to which a magnetic field is applied from the application unit 30. Therefore, by repeatedly applying and removing a magnetic field to the compounds 11 and 12, at least one of cooling and heating of the fluid can be performed.

[0073] (6-8) The magnetic refrigeration device 100 according to this embodiment includes a heat source 1 and a pump 63 as a moving part. The heat source 1 is the heat source according to (6-7) above. The pump 63 as a moving part moves a fluid that exchanges heat with a magnetic material (module 10 in this embodiment).

[0074] Here, the fluid heated by heat exchange with the magnetic material can be moved by the pump 63 as a moving part to extract hot heat, and the fluid that has absorbed heat by heat exchange with the magnetic material can be moved by the pump 63 as a moving part to extract cold heat.

[0075] (7) Variations The heat source 1 and the magnetic refrigeration device 100 described above include, but are not limited to, two or more types of compounds 11 and 12. The module and the magnetic refrigeration device of this modification include one type of compound. EXAMPLES

[0076] (Simulation method) In this example, the following three methods (a) to (c) were used as the simulation method.

[0077] (a)Akai KKR AkaiKKR is a method for performing first-principles electronic structure calculations based on density functional theory using Green's functions, and is also known as Machikaneyama (see "Introduction to Computational Materials Design", Osaka University Press).

[0078] Specifically, AkaiKKR is a program package for first-principles electronic state calculations based on the local density approximation (LDA) or generalized gradient approximation (GGA) of the density functional theory. AkaiKKR can easily calculate the electronic states of metals, semiconductors, compounds, etc., and is particularly useful as a first-principles calculation method that can handle alloys. AkaiKKR incorporates the coherent potential approximation (CPA), making it possible to handle not only regular ordered crystals, but also disordered systems such as impurity systems, disordered substitutional alloys, and mixed crystals.

[0079] (b) HiLAPW HiLAPW uses the FLAPW method, which is one of the first-principles electronic structure calculation methods based on density functional theory (see Uchida Rokakuho Publishing's "Band Theory" by Oguchi Tamio).

[0080] Specifically, HiLAPW is an application that implements a first-principles calculation method based on the all-electron calculation method and full potential method called the FLAPW method. The FLAPW method is known as a method that can accurately calculate energy because it uses the full potential, and is particularly suitable for comparing energies within a lattice.

[0081] (c) Monte Carlo simulation method The Monte Carlo simulation method is a general one, but the values ​​calculated using Akai KKR are used as the magnetic interactions between magnetic atoms, and the Potts model is used as the spin model. The entropy is estimated from the Monte Carlo simulation method.

[0082] Example 1 In Example 1, the performance index as a magnetic material of the Heusler compound and the temperature of the second-order phase transition were calculated by exhaustive calculation. The results are shown in Fig. 6. In Fig. 6, the vertical axis indicates the temperature of the second-order phase transition, and the horizontal axis indicates the performance index as a magnetic material. The performance evaluation is a value based on the state of electron spin, and the higher the value, the higher the performance.

[0083] In FIG. 6, a system S in which a second-order phase transition and a first-order phase transition occur was extracted, centering on a composition that exists in the target temperature range. The results are shown in FIG. 7. In FIG. 7, the vertical axis indicates the entropy change, and the horizontal axis indicates the temperature of the second-order phase transition. The entropy change is a negative value. In FIG. 7, the entropy change of MnAs is shown as a reference line L.

[0084] From FIG. 7, six points (candidate materials extracted in FIG. 7) with higher performance than the reference line L were extracted, and furthermore, the temperature of the second-order phase transition and the entropy change due to the electron spin were obtained by the Monte Carlo simulation method. As a result, in the Heusler structure, the compound containing the elements Cr, Co, Fe, and P with the same content ratio (composition ratio) showed the best results. The results are shown in FIG. 8. In FIG. 8, the vertical axis shows the entropy change due to the electron spin when no magnetic field is applied at 0.0 [T] and when a magnetic field of 1.0 [T] is applied, and the horizontal axis shows the temperature. As shown in FIG. 8, it can be seen that the four-element compound containing all the elements Cr, Co, Fe, and P shows an entropy change of about 23 [J / kgK] due to the second-order phase transition at 520 [K], which is the temperature of the second-order phase transition.

[0085] It should be noted that FIG. 8 shows calculated values, and the calculated values ​​are about 200K to 300K larger than the actual values, so FIG. 8 shows that about 500K is preferable.

[0086] The inventors have also determined that the martensitic transformation temperature of a quaternary compound containing all the elements Cr, Co, Fe, and P in the Heusler structure is 520K. This shows that this compound undergoes a first-order structural phase transition and a second-order magnetic phase transition in succession. Furthermore, the inventors have found that a first-order phase transition exhibits an entropy change equivalent to that of a second-order phase transition. This suggests that this compound exhibits an entropy change of approximately 46 [J / kgK] due to the successive occurrence of a first-order phase transition and a second-order phase transition.

[0087] Comparative Example 1 As Comparative Example 1, La(Fe 0.85 S 0.15 ) 13 The temperature of the second-order phase transition and the entropy change due to electron spin were obtained. The results are shown in Figure 9. Figure 9 corresponds to Figure 8, and the vertical axis shows the entropy change due to electron spin when no magnetic field is applied (0.0 [T]) and when a magnetic field of 1.0 [T] is applied, and the horizontal axis shows the temperature when a magnetic field of 1.0 [T] is applied. As shown in Figure 9, the temperature of the second-order phase transition of La(Fe 0.85 S 0.15 ) 13 It can be seen that the second-order phase transition of the four-element Heusler compound of Cr, Co, Fe and P exhibits an entropy change of about 14 [J / kgK] due to the second-order phase transition. Therefore, when only the second-order phase transition is taken into consideration, the entropy change amount in the second-order phase transition of the four-element Heusler compound of Cr, Co, Fe and P, which showed the best results in Example 1, is about 1.0 times that of the La(Fe 0.85 S 0.15 ) 13 It can be seen that this is higher than the entropy change in the second-order phase transition of

[0088] In addition, La(Fe 0.85 S 0.15 ) 13 The calculation results are only the entropy change of the second-order phase transition. However, the entropy change (about 46 [J / kgK]) of the four-element Heusler compound of Cr, Co, Fe and P, which showed the best result in Example 1, was about 46 [J / kgK], which was about 47 [J / kgK], and the entropy change of the La(Fe 0.85 S 0.15 ) 13It can be seen that this is more than three times the entropy change of 14 [J / kgK].

[0089] Example 2 In Example 2, the relationship between lattice size and the temperature of the second-order phase transition was investigated. Specifically, the temperatures of the second-order phase transition at various lattice sizes were obtained for a compound consisting of the elements Cr, Co, Fe, and P in a Heusler structure. The results are shown in FIG. 10. In FIG. 10, the vertical axis indicates the temperature of the second-order phase transition, and the horizontal axis indicates the expansion rate of the lattice size, with the lattice constants a, b being 3.905 [Å] and c being 5.756 [Å] as the reference (0).

[0090] 10, it can be seen that in a compound of the elements Cr, Co, Fe, and P in a Heusler structure, the temperature of the second-order phase transition can be increased by increasing the lattice size. This shows that the temperature of the second-order phase transition can be controlled to be substantially the same as the temperature of the first-order phase transition by adjusting the lattice size.

[0091] It has also been found that by introducing a fifth element between the lattice or substituting some of the lattice sites of the compound with the fifth element, adjusting the lattice size, and changing the temperature of the second-order phase transition, it is possible to realize a compound in which a first-order structural phase transition and a second-order magnetic phase transition occur successively.

[0092] Although the embodiments and examples of the present disclosure have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the present disclosure described in the claims. [Explanation of symbols]

[0093] 1: Heat source 10: Module 11, 12, 13, 14: Compound 30: Applicator 63: Pump (moving part) 100: Magnetic refrigeration device [Prior art documents] [Patent documents]

[0094] [Patent Document 1] JP 2008-150695 A

Claims

1. In the Heusler structure, containing four or more elements, Compound (11) in which a first-order structural phase transition and a second-order magnetic phase transition occur successively.

2. Contains all the elements Cr, Co, Fe and P, The compound of claim 1.

3. Further comprising a fifth element, The compound according to claim 2.

4. A first compound (11) according to any one of claims 1 to 3, A second compound (12) having a composition different from that of the first compound; 4. A magnetic material comprising:

5. a temperature of a second-order phase transition of the first compound and a temperature of a second-order phase transition of the second compound are different from each other; The magnetic material according to claim 4.

6. The first compound and the second compound are linked together. A module (10) according to claim 4.

7. The magnetic material according to claim 4; An application unit (30) that applies a magnetic field to the magnetic material; A heat source (1).

8. A heat source according to claim 7; A moving part (63) for moving a fluid that exchanges heat with the magnetic material; A magnetic refrigeration device (100).

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