Method for producing magnetic cooling material and magnetic cooling material

Abstract

FIELD: metallurgy.SUBSTANCE: method for producing a magnetic cooling material includes mixing first and second magnetic cooling materials to produce a third magnetic cooling material. The content A1 of the first material and the content A2 of the second material in the third material, calculated per 100 parts by weight of the sum of the contents of A1 and A2, satisfy the formulas, respectively: ((T2–TT) / (T2–T1))×100−20≤A1≤((T2–TT) / (T2–T1))×100+20 and ((T1–TT) / (T1–T2))×100−20≤A2≤((T1–TT) / (T1–T2)), where T1 is the magnetic transition temperature of the first material, K; T2 is the magnetic transition temperature of the second material, K; W1 is the half-width of the peak on the curve of change in magnetic entropy depending on temperature for the first material, K; W2 is the half-width of the peak on the curve of change in magnetic entropy depending on temperature for the second material, K; TT is the target magnetic transition temperature of the third material, K.EFFECT: production of a magnetic cooling material whose magnetic transition temperature can be adjusted.5 cl, 3 dwg, 4 tbl, 11 ex

Description

[0001] Field of technology to which the invention relates

[0002] The present invention relates to a magnetic cooling material whose magnetic transition temperature can be controlled with high precision, and to a method for producing said material.

[0003] Prior art of the invention

[0004] Fluorocarbons are ozone-depleting substances and global warming gases. Therefore, from an environmental perspective, new refrigeration / air conditioning systems that do not use any fluorocarbons are of great importance. Refrigerants that can replace fluorocarbons are being actively developed. However, no new refrigerant that offers satisfactory performance, cost, and safety has yet found practical application.

[0005] On the other hand, magnetic refrigeration systems are also relevant, which, unlike traditional cooling / air conditioning systems, utilize the change in entropy with increasing magnetic field (magnetocaloric effect, ΔS). Examples of materials characterized by a large absolute value of ΔS include Mn(As 1-x Sb x ) (PTL 1) and La(Fe 1-x Si x ) 13 H x (PTL 2). In particular, the first material is characterized by a very large ΔS of -30 J / kg⋅K and can be an excellent magnetic cooling material. However, since As, which is a component of Mn(As 1-x Sb x ), exhibits toxicity, this material is difficult to use in practice. La(Fe 1-x Si x ) 13 H x is the most promising substance, since it is characterized by ΔS equal to -25 J / kg⋅K, the second largest value after Mn(As 1-x Sb x), and its constituent elements are non-toxic and are not rare metals. The change in ΔS occurs only at a limited temperature in the vicinity of the material's Curie temperature (Tc), demonstrating the magnetocaloric effect; a single material can only operate at a specific temperature. This makes it impossible to develop a refrigeration system that requires achieving a temperature difference over a substantially wide range. Given the above, a specific method is used to change the material's operating temperature. A typical method involves replacing some of the components with another element(s).

[0006] These materials are required to operate at temperatures around room temperature (approximately -70 to +70°C). However, unlike traditional magnetic refrigeration, which has been used to generate very low temperatures difficult to achieve with gas cooling, at the above-mentioned operating temperature, the magnetocaloric effect weakens due to non-negligible lattice vibrations. An AMR (active magnetic regenerative) cycle has been developed that utilizes lattice vibrations as a heat storage effect, making it possible to create a refrigeration / air conditioning system that utilizes the magnetocaloric effect and operates at temperatures around room temperature.

[0007] In an AMR cycle, a vessel is filled with a magnetic cooling material with spaces that allow a coolant, such as water, to pass through it (called a bed). The coolant can flow through these spaces toward the hot end and the cold end. While the coolant is at the cold end, a magnetic field, such as a permanent magnet, is applied to the bed, thereby reducing the entropy of the magnetic cooling material and increasing its temperature. The coolant flows from the cold end toward the hot end. The coolant absorbs heat from the magnetic cooling material, and the coolant moves toward the hot end and releases heat at the hot end using a heat exchanger. The magnetic field of the permanent magnet is then removed, increasing the entropy of the magnetic cooling material and lowering the temperature.The coolant moves from the hot end to the cold end. The coolant is cooled by a magnetic cooling material as it moves toward the cold end. The cooled coolant absorbs heat through a heat exchanger. Repeating this cycle creates a temperature difference between the hot and cold ends, creating a refrigeration cycle.

[0008] In the AMR cycle, the temperature difference achievable with a single-composite material ranges from approximately 2 to 10 K and varies depending on the material. To achieve a large temperature difference, which is required for applications such as refrigerators and air conditioners, magnetic cooling materials with different magnetic transition temperatures (Tc) are stacked in a vessel so that the different materials are arranged in the order of decreasing magnetic transition temperatures (Tc) from the hot end to the cold end (cascade stacking), and heat exchange occurs between adjacent magnetic cooling materials. To realize heat exchange, the operating temperatures of adjacent magnetic cooling materials must overlap to a certain extent. Therefore, the Tc of each magnetic cooling material in the cascade must be adjusted, taking into account the half-width of the material.

[0009] Bibliography

[0010] Patent Literature

[0011] PTL 1: Japanese Patent Application JP2003-28532A

[0012] PTL 2: Japanese Patent Application JP2006-89839A

[0013] Essence of the invention

[0014] Technical problem

[0015] In order to improve the heat exchange efficiency of the AMR cycle using cascade filling, it is necessary to control the magnetic junction temperature (Tc) of each magnetic cooling material that makes up the cascade with increased precision. For example, in the case of La(Fe 1-x Si x ) 13 H x, which is a promising material, there is a possibility of process variations in the range of approximately 1 K relative to the target Tc, despite Tc control. When a material with a Tc deviating from the target value is used in an AMR device, the variation in Tc can degrade the cascade connection. This can result in degraded performance, such as an inability to achieve the target temperature difference or a longer time required to achieve the target temperature difference.

[0016] The present invention was made in response to the above-mentioned situation. In view of the above, the purpose of the present invention is to develop a method for producing a magnetic cooling material whose magnetic transition temperature can be controlled with high accuracy, and to produce a magnetic cooling material whose magnetic transition temperature can be controlled with high accuracy.

[0017] Problem solution

[0018] As a result of their intensive research to achieve the object, the inventors of the present invention have found that by mixing two or more magnetic cooling materials characterized by different magnetic transition temperatures and a ratio (transition temperature difference / half-width) of 0.9 or less in predetermined ratios, it is possible to adjust the magnetic transition temperature of the resulting magnetic cooling material to a target value with an accuracy in the range of 0.7 K. The present invention has been completed based on the above information.

[0019] Thus, the present invention provides the following means for achieving the objective [1] - [5].

[0020] [1] A method for producing a magnetic cooling material, comprising the steps of:

[0021] preparing a first magnetic cooling material that satisfies formula (1) and a second magnetic cooling material that is different from the first magnetic cooling material and satisfies formula (2); and

[0022] mixing the first magnetic cooling material and the second magnetic cooling material to obtain a third magnetic cooling material,

[0023] wherein the content A1 of the first magnetic cooling material and the content A2 of the second magnetic cooling material in the third magnetic cooling material, based on 100 parts by mass of the sum of the content A1 and the content A2, satisfy the formulas (3) and (4), respectively:

[0024] - 0.9 ≤ (T1- T2) / W1≤ 0.9 … (1)

[0025] - 0.9 ≤ (T1- T2) / W2≤ 0.9 … (2)

[0026] ((T2- T T ) / (T2- T1)) × 100 - 20 ≤ A1≤ ((T2- T T ) / (T2- T1)) × 100 + 20 … (3)

[0027] ((T1- T T ) / (T1- T2)) × 100 - 20 ≤ A2≤ ((T1- T T) / (T1- T2)) × 100 + 20 … (4)

[0028] where T1 represents the temperature, in units of K, of the magnetic transition of the first magnetic cooling material, T2 represents the temperature, in units of K, of the magnetic transition of the second magnetic cooling material, W1 represents the half-width of the peak, in units of K, in the curve of change in magnetic entropy depending on temperature for the first magnetic cooling material, W2 represents the half-width of the peak, in units of K, in the curve of change in magnetic entropy depending on temperature for the second magnetic cooling material, and T T represents the target temperature, in units of K, of the magnetic junction of the third magnetic cooling material.

[0029] [2] A method for producing a magnetic cooling material according to [1], wherein the first magnetic cooling material and / or the second magnetic cooling material is a material obtained by mixing two types of magnetic cooling materials, wherein for each of the two types of magnetic cooling materials, the absolute value of the quantity obtained by dividing the difference between the magnetic transition temperatures of said two types of magnetic cooling materials by the half-width of the peak on the curve of change in magnetic entropy depending on temperature is 0.9 or less.

[0030] [3] A method for producing a magnetic cooling material according to [1] or [2], wherein the first magnetic cooling material further satisfies formula (5), and the second magnetic cooling material further satisfies formula (6):

[0031] - 0.4 ≤ (T1- T2) / W1≤ 0.4 … (5)

[0032] - 0.4 ≤ (T1- T2) / W2≤ 0.4 … (6)

[0033] where T1 represents the temperature, in units of K, of the magnetic transition of the first magnetic cooling material, T2 represents the temperature, in units of K, of the magnetic transition of the second magnetic cooling material, W1 represents the half-width of the peak, in units of K, in the curve of change in magnetic entropy depending on temperature for the first magnetic cooling material, and W2 represents the half-width of the peak, in units of K, in the curve of change in magnetic entropy depending on temperature in the second magnetic cooling material.

[0034] [4] A method for producing a magnetic cooling material according to any one of [1] to [3], wherein the absolute value of the difference (T3- T T ) temperature (T3), in units of K, of the magnetic transition of the third magnetic cooling material and the target temperature (T T ), in units of K, the magnetic transition is 0.7 K or less.

[0035] [5] A magnetic cooling material comprising at least a first magnetic cooling material that satisfies formula (7) and a second magnetic cooling material that is different from the first magnetic cooling material and satisfies formula (8), wherein the absolute value of the difference between the magnetic transition temperature and the target magnetic transition temperature is 0.7 K or less:

[0036] - 0.9 ≤ (T1- T2) / W1≤ 0.9 … (7)

[0037] - 0.9 ≤ (T1- T2) / W2≤ 0.9 … (8)

[0038] where T1 represents the temperature, in units of K, of the magnetic transition of the first magnetic cooling material, T2 represents the temperature, in units of K, of the magnetic transition of the second magnetic cooling material, W1 represents the half-width of the peak, in units of K, in the curve of change in magnetic entropy depending on temperature for the first magnetic cooling material, and W2 represents the half-width of the peak, in units of K, in the curve of change in magnetic entropy depending on temperature for the second magnetic cooling material.

[0039] Beneficial effect of the invention

[0040] The present invention makes it possible to obtain a magnetic cooling material whose magnetic transition temperature (Tc) can be controlled with high accuracy.

[0041] Brief description of drawings

[0042] Fig. 1 is a graph showing the ΔS-T characteristics of the magnetic cooling materials of Example 1.

[0043] Fig. 2 is a graph showing the ΔS-T characteristics of the magnetic cooling materials of Comparative Example 1.

[0044] Fig. 3 is a graph showing the ΔS-T characteristics of the magnetic cooling materials of Example 9.

[0045] Detailed description of the invention

[0046] Method for producing magnetic cooling material

[0047] The method for producing a magnetic cooling material of the present invention comprises the following steps: preparing a first magnetic cooling material that satisfies the following formula (1) and a second magnetic cooling material that is different from the first magnetic cooling material and satisfies the following formula (2); and mixing the first magnetic cooling material and the second magnetic cooling material to obtain a third magnetic cooling material, wherein the content (A1) (parts by mass) of the first magnetic cooling material and the content (A2) (parts by mass) of the second magnetic cooling material in the third magnetic cooling material, based on 100 parts by mass of the sum of the content (A1) and the content (A2), satisfy the following formulas (3) and (4):

[0048] - 0.9 ≤ (T1- T2) / W1≤ 0.9 … (1)

[0049] - 0.9 ≤ (T1- T2) / W2≤ 0.9 … (2)

[0050] ((T2- T T) / (T2- T1)) × 100 - 20 ≤ A1≤ ((T2- T T ) / (T2- T1)) × 100 + 20 … (3)

[0051] ((T1- T T ) / (T1- T2)) × 100 - 20 ≤ A2≤ ((T1- T T ) / (T1- T2)) × 100 + 20 … (4)

[0052] where T1 represents the temperature (K) of the magnetic transition of the first magnetic cooling material, T2 represents the temperature (K) of the magnetic transition of the second magnetic cooling material, W1 represents the half-width (K) of the peak of the curve displaying the dependence of the change in magnetic entropy on the temperature in the first magnetic cooling material, W2 represents the half-width (K) of the peak of the curve displaying the dependence of the change in magnetic entropy on the temperature in the second magnetic cooling material, and T Trepresents the target temperature (K) of the magnetic transition of the third magnetic cooling material. To form a layer in an AMR device, magnetic cooling materials are placed in a container in order of decreasing magnetic transition temperature. Thus, for an AMR device, magnetic cooling materials with magnetic transition temperatures ranging from high to low are required. The target magnetic transition temperature (T T ) of the third magnetic cooling material is, for example, the magnetic transition temperature required for the material in the case of its formation of the AMR device layer.

[0053] Each of the first magnetic cooling material and the second magnetic cooling material for use in the method for producing a magnetic cooling material according to the present invention preferably comprises at least one alloy selected from the group consisting of an R-Fe-Si alloy (R is a rare earth element) and an R-Fe-Si-H alloy (R is a rare earth element), the main component of which has a NaZn type structure. 13, based on the requirement of being able to stably achieve a significant magnetocaloric effect in the room temperature range and not including a toxic element. The R-Fe-Si alloy can be produced by melting / casting and homogenization carried out in a conventional manner. The R-Fe-Si-H alloy can be produced by melting / casting, homogenization and hydrogenation carried out in a conventional manner. The content of the alloy(s) in each of the first magnetic cooling material and the second magnetic cooling material is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0054] R-Fe-Si alloy, the main component of which has a NaZn type structure 13 , includes, for example, an alloy containing as a main component the compound R 1 (Fe, Si) 13 (R 1 : 7.14 at.%), having a NaZn type structure 13In the preferred alloy composition, the R content 1 (R 1 represents at least one element selected from rare earth elements and Zr, and essentially includes La) is from 6 to 10 at.%, and the amount of Si is from 9 to 12 at.%, based on the total number of elements of the compound other than R 1 . Preferably, a series of alloys with different Curie temperatures (e.g. alloys containing the compound R as a main component) 1 (Fe, M, Si) 13 (R 1 : 7.14 at.%), having a NaZn type structure 13 ) is obtained by replacing part of Fe in the compound R 1 (Fe, Si) metal M (at least one element selected from the group consisting of Co, Mn, Ni, Al, Zr, Nb, W, Ta, Cr, Cu, Ag, Ga, Ti and Sn).

[0055] The alloy can be produced by melting the parent metal or alloy in a vacuum or inert gas atmosphere, preferably in an Ar atmosphere, and casting the melt into a flat mold or a vertical book-type chill mold, or by liquid quenching the melt or casting a strip. Preferably, the alloy can be obtained in powder form using fine spraying. Depending on the alloy composition, the cast alloy may consist of a primary α-Fe crystalline phase and an R-Si phase (R is a rare earth element). In this case, in order to form the R(Fe, Si) compound 13 (R is a rare earth element) The cast alloy can be homogenized for a given period of time (10 hours to 30 days, depending on the structural morphology) at a temperature near or below the decomposition temperature of the compound (approximately 900 to 1300°C, which greatly depends on the alloy composition).

[0056] After homogenization, the alloy's main component is now the R(Fe, Si) compound 13 , exhibits brittleness and can be easily ground into a powder with a particle size of several hundred microns or smaller by mechanical atomization. If hydrogen absorption is required, the alloy can be heat treated in a hydrogen atmosphere after coarse grinding or without it. Although the processing conditions vary according to the amount of hydrogen to be absorbed, it is generally preferable to carry out the heat treatment at a temperature of 200 to 500°C for a period of approximately 1 to 20 hours and a hydrogen partial pressure of approximately 0.1 to 0.5 MPa. After hydrogenation, the alloy is more brittle and is often in powder form with a particle size of several hundred microns or smaller when removed from the processing device.

[0057] The first magnetic cooling material for use in the method for producing the magnetic cooling material of the present invention satisfies the above formula (1), and the second magnetic cooling material for use in the method for producing the magnetic cooling material of the present invention satisfies the above formula (2). If the first magnetic cooling material does not satisfy the above formula (1), and the second magnetic cooling material does not satisfy the above formula (2), then the third magnetic cooling material obtained after mixing the first magnetic cooling material and the second magnetic cooling material will exhibit a bimodal peak in the curve displaying the entropy change versus temperature dependence (ΔS-T characteristic) in the third magnetic cooling material. Thus, the third magnetic cooling material clearly has two magnetic transition temperatures.As a result, this may lead to a decrease in the heat exchange efficiency of the AMR device filled with a magnetic cooling material in a cascade arrangement. From this perspective, it is preferable that the first magnetic cooling material additionally satisfies the following formula (5-1), and the second magnetic cooling material additionally satisfies the following formula (6-1). It is more preferable that the first magnetic cooling material additionally satisfies the following formula (5-2), and the second magnetic cooling material additionally satisfies the following formula (6-2). When the first magnetic cooling material and the second magnetic cooling material are used in combination, the value of ΔS is sometimes lower than in the case of using the first magnetic cooling material or the second magnetic cooling material separately.The reduction rate ΔS due to the combination of the first magnetic cooling material and the second magnetic cooling material can be reduced when the first magnetic cooling material and the second magnetic cooling material satisfy the following formulas:.

[0058] - 0.4 ≤ (T1- T2) / W1≤ 0.4 … (5-1)

[0059] - 0.4 ≤ (T1- T2) / W2≤ 0.4 … (6-1)

[0060] - 0.2 ≤ (T1- T2) / W1≤ 0.2 … (5-2)

[0061] - 0.2 ≤ (T1- T2) / W2≤ 0.2 … (6-2)

[0062] where T1 represents the temperature (K) of the magnetic transition of the first magnetic cooling material, T2 represents the temperature (K) of the magnetic transition of the second magnetic cooling material, W1 represents the half-width of the peak (K) in the curve displaying the ΔS-T characteristics of the first magnetic cooling material, and W2 represents the half-width of the peak (K) in the curve displaying the ΔS-T characteristics of the second magnetic cooling material.

[0063] The ΔS-T characteristics of the magnetic cooling material can be determined as follows. Using a vibrating sample magnetometer (VSM), the magnetic moment (M) of the magnetic cooling material is measured at temperatures varying from high to low under the influence of a magnetic field that is stepwise increased from 0 T to 1 T at 0.2 T intervals to determine the exact relationship (M (T, H)) of the magnetic moment (M) with temperature (T) and magnetic field strength (H). These results are substituted into the following equation to obtain the ΔS-T characteristics of the magnetic cooling material:

[0064]

[0065] The half-width (K) of the peak of the curve displaying the ΔS-T characteristics of the magnetic cooling material is defined in this document as follows. If the ΔS value at the top of the peak of the curve displaying the ΔS-T characteristics is represented by the ΔS value Max, the half-width is defined as the absolute value of the difference (T a - T b ) two temperatures (T a , T b ), at which the value of ΔS at the peak is half the value of ΔS Max .

[0066] A third magnetic cooling material is obtained by mixing the first magnetic cooling material and the second magnetic cooling material. The content (A1) (parts by mass) of the first magnetic cooling material and the content (A2) (parts by mass) of the second magnetic cooling material in the third magnetic cooling material, based on 100 parts by mass of the total content (A1) and the content (A2), satisfy the above formulas (3) and (4). If the content (A1) (parts by mass) of the first magnetic cooling material and the content (A2) (parts by mass) of the second magnetic cooling material do not satisfy the above formulas (3) and (4), the magnetic transition temperature of the third magnetic cooling material sometimes cannot be accurately adjusted to the target magnetic transition temperature (T T ). The absolute value of the difference (T3- T T) temperature (T3) (K) of the magnetic transition of the third magnetic cooling material and the target temperature (T T ) of the magnetic transition temperature is, for example, 0.7 K or less, preferably 0.5 K or less, and more preferably 0.3 K or less. The determination of the magnetic transition temperature includes a measurement error of about ±0.2°C; therefore, in the above formulas (3) and (4), there may be an error of about 20 parts by mass. However, an error of 20 parts by mass or less has little influence on the system. In view of the above, a value of 20 is subtracted and added in each of the above formulas (3) and (4). There is no particular limitation regarding the mixing method of the first magnetic cooling material and the second magnetic cooling material. For example, mixing can be performed in a V-shaped mixer.

[0067] From the viewpoint of more accurately controlling the magnetic transition temperature of the third magnetic cooling material, the content (A1) (parts by mass) of the first magnetic cooling material and the content (A2) (parts by mass) of the second magnetic cooling material in the third magnetic cooling material, based on 100 parts by mass of the total content (A1) and the content (A2), preferably satisfy the following formulas (3-1) and (4-1), more preferably satisfy the following formulas (3-2) and (4-2), even more preferably satisfy the following formulas (3-3) and (4-3), and still more preferably satisfy the following formulas (3-4) and (4-4).

[0068] ((T2- T T ) / (T2- T1)) × 100 - 10 ≤ A1≤ ((T2- T T ) / (T2- T1)) × 100 + 10 … (3-1)

[0069] ((T1- T T ) / (T1- T2)) × 100 - 10 ≤ A2≤ ((T1- T T ) / (T1- T2)) × 100 + 10 … (4-1)

[0070] ((T2- T T) / (T2- T1)) × 100 - 5 ≤ A1≤ ((T2- T T ) / (T2- T1)) × 100 + 5 … (3-2)

[0071] ((T1- T T ) / (T1- T2)) × 100 - 5 ≤ A2≤ ((T1- T T ) / (T1- T2)) × 100 + 5 … (4-2)

[0072] ((T2- T T ) / (T2- T1)) × 100 - 3 ≤ A1≤ ((T2- T T ) / (T2- T1)) × 100 + 3 … (3-3)

[0073] ((T1- T T ) / (T1- T2)) × 100 - 3 ≤ A2≤ ((T1- T T ) / (T1- T2)) × 100 + 3 … (4-3)

[0074] ((T2- T T ) / (T2- T1)) × 100 - 1 ≤ A1≤ ((T2- T T ) / (T2- T1)) × 100 + 1 … (3-4)

[0075] ((T1- T T ) / (T1- T2)) × 100 - 1 ≤ A2≤ ((T1- T T ) / (T1- T2)) × 100 + 1 … (4-4)

[0076] Either one of the first magnetic cooling material or the second magnetic cooling material may be a material obtained by mixing two types of magnetic cooling materials, or each of the first magnetic cooling material and the second magnetic cooling material may be a material obtained by mixing two types of magnetic cooling materials. In this case, in each of the two types of magnetic cooling materials constituting the first magnetic cooling material or the second magnetic cooling material, the absolute value of the value obtained by dividing the difference in the magnetic transition temperature of the two types of magnetic cooling materials by the half-width of the peak of the curve displaying the change in magnetic entropy as a function of temperature is preferably 0.9 or less, more preferably 0.4 or less, and even more preferably 0.2 or less.

[0077] In the case of the magnetic cooling material obtained by the above method, the deviation of the magnetic transition temperature from the target magnetic transition temperature (T T ) can be adjusted in the range of 0.7 K. This magnetic cooling material can sufficiently satisfy the accuracy of achieving the magnetic transition temperature required for the material when used in the AMR cycle.

[0078] Magnetic cooling material

[0079] The magnetic cooling material of the present invention comprises at least a first magnetic cooling material that satisfies the following formula (7-1), preferably satisfies the following formula (7-2), and a second magnetic cooling material that is different from the first magnetic cooling material and satisfies the following formula (8-1), preferably satisfies the following formula (8-2). The absolute value of the difference between the magnetic transition temperature and the target magnetic transition temperature is 0.7 K or less, preferably 0.5 K or less, and more preferably 0.3 K or less.

[0080] - 0.9 ≤ (T1- T2) / W1≤ 0.9 … (7-1)

[0081] - 0.4 ≤ (T1- T2) / W1≤ 0.4 … (7-2)

[0082] - 0.9 ≤ (T1- T2) / W2≤ 0.9 … (8-1)

[0083] - 0.4 ≤ (T1- T2) / W2≤ 0.4 … (8-2)

[0084] where T1 represents the temperature (K) of the magnetic transition of the first magnetic cooling material, T2 represents the temperature (K) of the magnetic transition of the second magnetic cooling material, W1 represents the half-width (K) of the peak of the curve displaying the dependence of the change in magnetic entropy on the temperature in the first magnetic cooling material, and W2 represents the half-width (K) of the peak of the curve displaying the dependence of the change in magnetic entropy on the temperature in the second magnetic cooling material.

[0085] The first magnetic cooling material and the second magnetic cooling material of the magnetic cooling material of the present invention are the same as those described above with reference to the method for producing the magnetic cooling material of the present invention; in view of the above, the description of the first magnetic cooling material and the second magnetic cooling material in the magnetic cooling material of the present invention will be omitted.

[0086] The magnetic cooling material of the present invention may comprise a magnetic cooling material other than the first magnetic cooling material and the second magnetic cooling material, as long as the use of said other material does not weaken the effect of the present invention.

[0087] Examples

[0088] The following examples explain the present invention in more detail and do not limit the scope of the invention in any way.

[0089] ΔS-T characteristics of magnetic cooling material

[0090] The dependence of the magnetic moment of the magnetic cooling material on temperature and magnetic field was determined using a vibrating sample magnetometer (VSM) (Versa Lab, manufactured by Quantum Design, Inc.). The ΔS-T characteristics of the magnetic cooling material were obtained based on the measurement results by the method described above. The decrease rate of ΔS was calculated, which is expressed by the following formula: ((ΔS av- ΔS3) / ΔS av × 100) (%), in which ΔS av represents the arithmetic mean of the ΔS value (ΔS1) at the apex of the peak of the curve displaying the ΔS-T characteristic of the first magnetic cooling material and the ΔS value (ΔS2) at the apex of the peak of the curve displaying the ΔS-T characteristic of the second magnetic cooling material, and ΔS3 represents the ΔS value at the apex of the peak of the curve displaying the ΔS-T characteristic of the third magnetic cooling material.

[0091] Example 1

[0092] Alloy 1 and alloy 2 having the compositions shown in Table 1 were prepared. These alloys were subjected to heat treatment at 1160°C for 50 hours to homogenize them, followed by hydrogenation for 8 hours at a temperature of 450°C and a pressure of 0.27 MPa, thereby obtaining a first magnetic cooling material of alloy 1 and a second magnetic cooling material of alloy 2. The first magnetic cooling material and the second magnetic cooling material were intentionally designed to have different magnetic transition temperatures by using different Fe contents and different Mn contents in the two magnetic cooling materials.Table 2 shows the magnetic transition temperatures of the first magnetic cooling material and the second magnetic cooling material, and also presents the values ​​(magnetic transition temperature difference / half-width), each of which is obtained by dividing the magnetic transition temperature difference between the first magnetic cooling material and the second magnetic cooling material by the half-width. The mixing amounts of the first magnetic cooling material and the second magnetic cooling material were determined using the following equations (9) and (10) so that the magnetic transition temperature of the third magnetic cooling material obtained by mixing the first magnetic cooling material and the second magnetic cooling material was 298.8 K (target magnetic transition temperature).The magnetic transition temperature and the decrease rate of ΔS of the obtained third magnetic cooling material are given in Table 2, and the ΔS-T characteristics of the third magnetic cooling material are shown in Fig. 1.

[0093] Mixing amount (% by mass) of the first magnetic cooling material = ((T2- T T ) / (T2- T1)) × 100 … (9)

[0094] Mixing amount (% by mass) of the second magnetic cooling material = ((T1- T T ) / (T1- T2)) × 100 … (10)

[0095] where T1 represents the temperature (K) of the magnetic transition of the first magnetic cooling material, T2 represents the temperature (K) of the magnetic transition of the second magnetic cooling material, and T T represents the target temperature (K) of the magnetic transition.

[0096] Comparative Example 1

[0097] Alloy 1 and alloy 2 having the compositions shown in Table 1 were prepared. These alloys were processed in the same way as in Example 1 to obtain a first magnetic cooling material made of alloy 1 and a second magnetic cooling material made of alloy 2. The first magnetic cooling material and the second magnetic cooling material were intentionally created to be able to obtain different magnetic transition temperatures by using different Mn contents in the two magnetic cooling materials. Table 2 shows the magnetic transition temperatures and values ​​​​(the ratio of the difference in magnetic transition temperature to the half-width) related to the first magnetic cooling material and the second magnetic cooling material.The mixing amounts of the first magnetic cooling material and the second magnetic cooling material were determined using the above equations (9) and (10) so that the magnetic transition temperature of the third magnetic cooling material obtained by mixing the first magnetic cooling material and the second magnetic cooling material was 295.6 K (target magnetic transition temperature). The magnetic transition temperature and the decrease rate of the ΔS value of the obtained third magnetic cooling material are shown in Table 2, and the ΔS-T characteristics of the third magnetic cooling material are shown in Fig. 2.

[0098] Examples 2 - 8

[0099] Alloy 1 and alloy 2 having the composition shown in Table 1 were prepared. These alloys were subjected to the same processing as in Example 1 to obtain a first magnetic cooling material of alloy 1 and a second magnetic cooling material of alloy 2. The first magnetic cooling material and the second magnetic cooling material are designed to be able to obtain different magnetic transition temperatures by using different Fe contents and different Mn contents in the two magnetic cooling materials. Table 2 shows the magnetic transition temperature and the value (the ratio of the difference in magnetic transition temperature to the half-width) related to the first magnetic cooling material and the second magnetic cooling material.The mixing amounts of the first magnetic cooling material and the second magnetic cooling material were determined using the above equations (9) and (10) so that the third magnetic cooling material obtained by mixing the first magnetic cooling material and the second magnetic cooling material was characterized by the target magnetic transition temperature given in Table 2. The magnetic transition temperature and the rate of decrease in the ΔS value of the obtained third magnetic cooling material are presented in Table 2.

[0100] Example 9

[0101] In Example 9, the third magnetic cooling material obtained in Example 6 was used as the first magnetic cooling material, and the third magnetic cooling material obtained in Example 7 was used as the second magnetic cooling material. Table 2 shows the magnetic transition temperature and the value (the ratio of the difference in magnetic transition temperature to the half-width) of the first magnetic cooling material and the second magnetic cooling material. The mixing amounts of the first magnetic cooling material and the second magnetic cooling material were determined using the above equations (9) and (10) so that the third magnetic cooling material obtained by mixing the first magnetic cooling material and the second magnetic cooling material had the target magnetic transition temperature shown in Table 2.The magnetic transition temperature and the decrease rate of ΔS of the obtained third magnetic cooling material are shown in Table 2, and the ΔS-T characteristics of the third magnetic cooling material are shown in Fig. 3.

[0102] Comparative Example 2

[0103] A third magnetic cooling material was obtained in the same manner as in Example 1, except that the mixing amount of the first magnetic cooling material was replaced with an amount that was 40% smaller than the mixing amount determined according to the above equation (9), and that the mixing amount of the second magnetic cooling material was replaced with an amount that was 40% larger than the mixing amount determined according to the above equation (10). The magnetic transition temperature and the decrease rate of the ΔS value of the obtained third magnetic cooling material are shown in Table 2.

[0104] Table 1

[0105] Composition of alloy 1 (the first magnetic cooling material) [at.%] Alloy composition 2 (second magnetic cooling material) [at.%] La Ce Fe Al Mn Si La Ce Fe Al Mn Si Example 1 5,26 2,26 81,36 0,00 0,95 10,17 5,26 2,26 81,44 0,00 0,87 10,17 Example 2 5,26 2,26 81,88 0,00 0,43 10,17 5,26 2,26 81,85 0,00 0,46 10,17 Example 3 5,26 2,26 80,83 0,00 1,48 10,17 5,26 2,26 80,91 0,00 1,40 10,17 Example 4 5,26 2,26 81,88 0,00 0,43 10,17 5,26 2,26 81,85 0,00 0,46 10,17 Example 5 5,26 2,26 80,98 0,00 1,33 10,17 5,26 2,26 80,91 0,00 1,40 10,17 Example 6 5,26 2,26 82,05 0,00 0,26 10,17 5,26 2,26 82,10 0,00 0,21 10,17 Example 7 5,26 2,26 82,25 0,00 0,06 10,17 5,26 2,26 82,31 0,00 0,00 10,17 Example 8 7,27 0,00 82,53 3,71 0,04 6,49 7,27 0,00 82,53 3,71 0,00 6,49 Comparative example 1 5,26 2,26 81,36 0,00 1,03 10,17 5,26 2,26 81,36 0,00 0,95 10,17 Comparative example 2 5,26 2,26 81,36 0,00 0,95 10,17 5,26 2,26 81,44 0,00 0,87 10,17

[0106]

[0107] These results show that by mixing the first magnetic cooling material and the second magnetic cooling material in mixing amounts that satisfy the above formulas (3) and (4), a third magnetic cooling material can be obtained that has a target magnetic transition temperature with an accuracy of 0.7K or less relative to the target magnetic transition temperature. Therefore, the results indicate that the magnetic transition temperature of the third magnetic cooling material can be controlled with high accuracy.These results also show that the rate of decrease in ΔS is high in Examples 3 and 9 in which the values ​​of (magnetic transition temperature difference / half-width) are greater than 0.4 and 0.9 or less, while the rate of decrease in ΔS is significantly lower in Examples in which the values ​​of (magnetic transition temperature difference / half-width) are 0.4 or less.

[0108] Fig. 1 shows the ΔS-T characteristics of the magnetic cooling materials of Example 1. Since the values ​​of the quantity (magnetic transition temperature difference / half-width) related to the first magnetic cooling material and the second magnetic cooling material are 0.9 or less, the curve displaying the ΔS-T characteristics of the third magnetic cooling material has a monomodal peak rather than a bimodal peak.

[0109] Figure 2 shows the ΔS-T characteristics of the magnetic cooling materials of Comparative Example 1. Since the values ​​of (magnetic transition temperature difference / half-width) related to the first magnetic cooling material and the second magnetic cooling material are greater than 0.9, the curve representing the ΔS-T characteristics of the third magnetic cooling material has a bimodal peak. Therefore, it is impossible to specify a single magnetic transition temperature characteristic of the third magnetic cooling material. When the third magnetic cooling material has multiple magnetic transition temperatures, it is difficult to apply it as a magnetic cooling material cascaded in an AMR device.

[0110] Fig. 3 shows the ΔS-T characteristics of the magnetic cooling materials of Example 9. The values ​​of (magnetic transition temperature difference / half-width) related to the first magnetic cooling material and the second magnetic cooling material are 0.8, and the decrease rate of the ΔS value is high. Since the values ​​of (magnetic transition temperature difference / half-width) are 0.9 or less, the curve displaying the ΔS-T characteristics of the third magnetic cooling material has a unimodal peak rather than a bimodal peak. The deviation of the measured magnetic transition temperature of the third magnetic cooling material from the target magnetic transition temperature is 0.7 K or less.

[0111] In Comparative Example 2, the mixing amounts of the first magnetic cooling material and the second magnetic cooling material do not satisfy the above formulas (3) and (4); taking into account the above, the deviation of the measured magnetic transition temperature of the third magnetic cooling material from the target magnetic transition temperature reaches 0.8 K.

Claims

1. A method for producing a magnetic cooling material, comprising the following stages: preparing a first magnetic cooling material that satisfies formula (1) and a second magnetic cooling material that is different from the first magnetic cooling material and satisfies formula (2); and mixing the first magnetic cooling material and the second magnetic cooling material to obtain a third magnetic cooling material, wherein the content A1 of the first magnetic cooling material and the content A2 of the second magnetic cooling material in the third magnetic cooling material, calculated per 100 parts by weight of the sum of the content A1 and the content A2, satisfy formulas (3) and (4), respectively: −0.9≤(T1−T2) / W1≤0.9 (1) −0.9≤(T1−T2) / W2≤0.9 (2) ((T2–T T ) / (T2–T1))×100−20≤A1≤((T2–T T ) / (T2–T1))×100+20 (3) ((T1–T T ) / (T1–T2))×100−20≤A2≤((T1–T T) / (T1–T2))×100+20 (4), where T1 represents the temperature, in units of K, of the magnetic junction of the first magnetic cooling material; T2 represents the temperature, in units of K, of the magnetic junction of the second magnetic cooling material; W1 represents the half-width of the peak, in units of K, on ​​the magnetic entropy versus temperature curve for the first magnetic cooling material; W2 represents the half-width of the peak, in units of K, on ​​the magnetic entropy versus temperature curve for the second magnetic cooling material; T T represents the target temperature, in units of K, of the magnetic junction of the third magnetic cooling material.

2. A method for producing a magnetic cooling material according to claim 1, wherein the first magnetic cooling material and / or the second magnetic cooling material is a material obtained by mixing two types of magnetic cooling materials, wherein for each of the two types of magnetic cooling materials, the absolute value of the quantity obtained by dividing the difference between the magnetic transition temperatures of said two types of magnetic cooling materials by the half-width of the peak on the curve of change in magnetic entropy depending on temperature is 0.9 or less.

3. A method for producing a magnetic cooling material according to claim 1 or 2, wherein the first magnetic cooling material additionally satisfies formula (5), and the second magnetic cooling material additionally satisfies formula (6): −0.4≤(T1−T2) / W1≤0.4 (5) −0.4≤(T1−T2) / W2≤0.4 (6), where T1 represents the temperature, in units of K, of the magnetic junction of the first magnetic cooling material; T2 represents the temperature, in units of K, of the magnetic junction of the second magnetic cooling material; W1 represents the half-width of the peak, in units of K, on ​​the magnetic entropy versus temperature curve for the first magnetic cooling material; W2 represents the half-width of the peak, in units of K, in the curve of magnetic entropy versus temperature in the second magnetic cooling material.

4. A method for producing a magnetic cooling material according to any one of paragraphs 1-3, in which the absolute value of the difference (T3−T T ) temperature (T3), in units of K, of the magnetic transition of the third magnetic cooling material and the target temperature (T T ), in units of K, the magnetic transition is 0.7 K or less.

5. A magnetic cooling material comprising at least a first magnetic cooling material that satisfies formula (7) and a second magnetic cooling material that is different from the first magnetic cooling material and satisfies formula (8), wherein the absolute value of the difference between the magnetic transition temperature and the target magnetic transition temperature is 0.7 K or less: −0.9≤(T1−T2) / W1≤0.9 (7) −0.9≤(T1−T2) / W2≤0.9 (8), where T1 represents the temperature, in units of K, of the magnetic junction of the first magnetic cooling material; T2 represents the temperature, in units of K, of the magnetic junction of the second magnetic cooling material; W1 represents the half-width of the peak, in units of K, on ​​the magnetic entropy versus temperature curve for the first magnetic cooling material; W2 represents the half-width of the peak, in units of K, in the magnetic entropy versus temperature curve for the second magnetic cooling material.

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