Magnetic refrigeration material and magnetic refrigeration device using the same

Abstract

To search for magnetic refrigeration materials in which a huge MCE|▵Sm| that does not cause thermal hysteresis indicates 17 [J / (kg K)] or more in a temperature zone of 40-170K including a liquid nitrogen temperature of around 77K required for gas liquefaction.SOLUTION: A magnetic refrigeration material comprises Gd (gadolinium), Ge (germanium), Sn (tin), Si (silicon), and unavoidable impurities, and has a composition represented by the following compositional formula: Gd5Ge4-x-zSnxSiz: 1.6<x<2.4, 0<z<1.3. The material has a transition temperature Ttr of magnetic phase transition in a temperature range of 80K to 170K, and exhibits a secondary magnetic phase transition in a range of 20K before and after the transition temperature Ttr. A magnetic refrigeration material also comprises Gd (gadolinium), Dy (dysprosium), Ge (germanium), Sn (tin), and unavoidable impurities, and has a composition represented by the following compositional formula: Gd5-yDyySnxGe4-x: 1.6<x<2.4, 0<y<1.1.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a magnetic refrigeration material and a magnetic refrigeration device using the same. [Background technology]

[0002] In recent years, there has been an increasing demand for gas consumption and production in all market segments, including natural gas, oxygen, nitrogen and hydrogen. However, gases in the gaseous state are bulky and require liquefaction for storage and transportation. Traditional liquefaction methods require energy-intensive gas compression processes at cryogenic temperatures, which are very inefficient at temperatures below 150 K. Magnetic refrigeration (MR) technology based on the magnetocaloric effect (MCE) can be a radically different alternative to conventional gas compression cooling technology because it is ideally highly efficient and environmentally friendly. To achieve this, magnetic refrigerant materials with large MCE in the temperature region of interest from 20 to 150 K are required to liquefy gases such as hydrogen, nitrogen, oxygen, and natural gas. However, as shown in Fig. 9, in the wide temperature range from 60 K to 150 K required for gas liquefaction, the entropy change △S of currently known MR materials in this wide temperature range is 10 to 20 [J / (kg K)]. Therefore, the fact that no MR materials with a huge MCE, with a △S of about 30 to 40 [J / (kg K)] required for gas liquefaction, are known is a bottleneck in the practical application of MR cooling systems.

[0003] In Patent Document 1, a magnetic refrigeration working material is sought that utilizes a large magnetic entropy change caused by an external magnetic field near the Curie temperature of the ferromagnetic-paramagnetic transition in a temperature range of 20 to 300 K. The publication states that an amorphous alloy or a multi-phase microcrystal aggregate alloy produced by quenching a melt consisting of rare earth elements Gd, Tb, Dy, Ho, and Er with large magnetic moments, one or more of Zr, Hf, Al, Si, and Ge as amorphous elements, and Cu, Ni, and Ag as elements that increase affinity with the cooling bodies Cu and Ag in a vacuum or in an inert gas atmosphere with a Cu or Ag cooling body controlled at a temperature of room temperature to 850 K, provides a working material with large magnetic entropy over a wide temperature range and excellent magnetic refrigeration performance. However, the magnetic refrigeration material having the composition disclosed in the examples of the elemental composition disclosed in Patent Document 1 has a small magnetic entropy change and is not suitable for practical use in commercial hydrogen liquefaction devices using magnetic refrigeration. In other words, it was necessary to further search for a magnetic refrigeration material having an optimal elemental composition from the abstract elemental composition disclosed in Patent Document 1.

[0004] In Patent Document 2, the following thermomagnetic material is described as a thermomagnetic material for a heat exchanger: Gd5(Si x Ge 1-x )4, (0.2≦x≦1) (V), Tb5(Si 4-x Ge x ), (x=0, 1, 2, 3, 4) (VI), XTiGe, (X=Dy, Ho, Tm) (VII) has been proposed, but examples are limited to MnFePGe and MnFePGeSb systems. In addition, the thermomagnetic materials in the examples disclosed in Patent Document 2 have Curie temperatures of 240 to 340 K, and no magnetic refrigerant material is disclosed that has a large MCE in the temperature range of interest of 15 to 150 K, which is required for a hydrogen liquefaction device using magnetic refrigeration.

[0005] Second-order magnetic phase transition (SOMT) materials, which have essentially no thermal hysteresis, are expected to be good candidates for this application due to their reversible MCE and excellent mechanical stability during cycling. Ho-based SOMT compounds, such as HoB2, HoN, and HoNi2, exhibit giant MCE (-△S m >20[J / (kg·K)]) has been achieved, but it is impossible to maintain such a huge MCE down to 60K. For example, in ErAl2 and HoN compounds, |△Sm| decreases to 37 [J / (kg·K)] and 29 [J / (kg·K)] at temperatures below 20 K, and to 18 [J / (kg·K)] and 11 [J / (kg·K)] at 60 K. Furthermore, in TbAl2, it deteriorates to 14 [J / (kg·K)] at 90 K, and in (Gd,Tb)Al2 compounds, it deteriorates to 11 [J / (kg·K)] at 140 K. Therefore, there are very few refrigerant materials that show a huge MCE |△Sm| of 20 [J / (kg·K)] or more without thermal hysteresis at temperatures of 60 to 150 K required for gas liquefaction.

[0006] In addition, Patent Documents 3 and 4 propose ErCo2-based magnetocaloric effect compounds as second order magnetic phase transition (SOMT) materials. 2-y (Fe, Mn) y (0.02≦y≦0.07) is proposed. 2-x-y Ai x Ni y (0 <x≦0.1、0≦y≦0.2)、ErCo 2-x-y Fe x Ni y (0.035≦x≦0.1, 0≦y≦0.2) has been proposed. These ErCo2-based magnetocaloric effect compounds include, for example, ErCo 1.96 Fe 0.04 At 50K, |△Sm| is about 0.2 J / (cm -3 ·K), and the specific gravity of ErCo2 is about 10g / cm 3If so, it corresponds to approximately 20 [J / (kg·K)]. However, in the temperature range near the liquid nitrogen temperature of 77K required for gas liquefaction, as a refrigerant material that does not cause thermal hysteresis and shows a large magnetocaloric effect (MCE) |△Sm| of 20 [J / (kg·K)] or more, there is a shortage in the bandwidth, and it is necessary to search for new magnetocaloric effect compounds in the temperature range near the liquid nitrogen temperature of 77K.

[0007] On the other hand, first-order magnetic phase transition (FOMT) substances show a large MCE, and this large MCE can be maintained over a wide temperature range. For example, Gd5(Si x Ge 1-x )4 (0 < x < 0.5) shows a large MCE (-△S m of 20 [J / (kg·K)] or more) in a wide temperature range from 20K to 290K. However, the Gd5(Si x Ge 1-x )4 compounds related to FOMT are troubled by irreversible MCE due to thermal hysteresis and mechanical instability, which hinders their practical application. So far, a great deal of effort has been devoted to reducing the hysteresis of Gd5(Si x Ge 1-x )4 compounds, and it has been found that the reduction of hysteresis in SOMT materials is achieved at the expense of |△Sm|. For example, the |△Sm| of Gd5Si2Ge2 decreases to that of Gd5Si2Ge 1.9 Fe 0.1 of 7J / cm 3 K under a magnetic field change of 5T that minimizes hysteresis. Therefore, the Gd5Si2Ge2-based compounds have the problem of not being very attractive for practical application.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

[0009] As described above, in the temperature range of 40K - 170K including the vicinity of the liquid nitrogen temperature of 77K required for gas liquefaction, a large magnetocaloric effect (MCE) |△Sm| that does not cause thermal hysteresis is 17 [J / (kg·K)] or more, more preferably 20 [J / (kg·K)] or more. The problem is to search for a refrigerant material and provide a new material for magnetic refrigeration. [Means for Solving the Problems]

[0010] The inventor considered that Gd5Ge4 could be a promising candidate for gas liquefaction at low temperatures due to its large magnetocaloric effect (|△Sm| = 25 [J / (kg·K)]) at 50K and large refrigeration capacity. However, the large thermal hysteresis up to 5K due to the nature of FOMT (Figure 1(c)) hinders its practical application for gas liquefaction. Therefore, by searching for Gd5Ge4 - based compounds added with a third element, it was considered that a large magnetocaloric effect at 50K near the liquid nitrogen temperature and a second - order magnetic phase transition (SOMT) material could coexist, and the third element added to the Gd5Ge4 - based compound was searched. Furthermore, Sn was selected as this third element, and when searching for the fourth element added to the Gd5Ge 4-x Sn x - Sn - based compound, the present invention was conceived.

[0011] [1] The magnetic refrigeration material of the present invention is composed of, for example, as shown in Table 6, Gd (gadolinium), Ge (germanium), Sn (tin), Si (silicon), and inevitable impurities, and has the following composition formula: Gd5Ge 4-x-z Sn x Si z : with a composition of 0.8 < x < 2.4, 0 < z < 1.3. [2] In the embodiments of the present invention, for the magnetic refrigeration material [1], the transition temperature T of the magnetic phase transition tr is within the temperature range of 80K to 170K, and shows a second-order magnetic phase transition within a range of 20K before and after the transition temperature T tr , or may show the characteristics of the boundary region between the second-order magnetic phase transition and the first-order magnetic phase transition. [3] The magnetic refrigeration material of the present invention consists of Gd (gadolinium), Dy (dysprosium), Ge (germanium), Sn (tin) and inevitable impurities, and has the following composition formula: Gd 5-y Dy y Sn x Ge 4-x : having a composition of 1.6 < x < 2.4, 0 < y < 1.1. [4] In the embodiments of the present invention, for the magnetic refrigeration material [3], Gd 5-y Dy y Sn2Ge2: may have a composition of 0 < y < 1.1. [5] In the embodiments of the present invention, for the magnetic refrigeration material [3] or [4], the transition temperature T of the magnetic phase transition tr is within the temperature range of 35K to 75K, and shows a second-order magnetic phase transition within a range of 20K before and after the transition temperature T tr , or may show the characteristics of the boundary region between the second-order magnetic phase transition and the first-order magnetic phase transition.

[0012] [6] In the embodiments of the present invention, for the magnetic refrigeration materials [1] to [5], within a range of 20K before and after the transition temperature T tr , the magnetic entropy change ΔS may be obtained to be 17 [J / (kg·K)] or more under a 5T magnetic field. [7] In the embodiments of the present invention, for the magnetic refrigeration material [6], under a 5T magnetic field, the magnetic entropy change ΔS may be obtained to be 20 [J / (kg·K)] or more. In this case, Gd5Ge 4-x-z Sn x Si z : preferably has a composition of 1.6 < x < 2.4, 0 < z < 1.1, and also Gd 5-y Dyy Sn x Ge 4-x may have a composition of 1.6 < x < 2.4 and 0 < y < 0.8. In addition, in the magnetic refrigeration material [6], even when the magnetic entropy change ΔS is 25 [J / (kg·K)] or more under a 5T magnetic field, it may be acceptable. In this case, Gd5Ge 4-x-z Sn x Si z it is preferably to have a composition of 1.6 < x < 2.4 and 0 < z < 0.9. Also, Gd 5-y Dy y Sn x Ge 4-x it may have a composition of 1.8 ≦ x ≦ 2.2 and 0 < y < 0.4. In addition, in the magnetic refrigeration material [6], even when the magnetic entropy change ΔS is 30 [J / (kg·K)] or more under a 5T magnetic field, it may be acceptable. In this case, Gd5Ge 4-x-z Sn x Si z it is preferably to have a composition of 1.6 < x < 2.4 and 0 < z ≦ 0.4. Also, Gd 5-y Dy y Sn x Ge 4-x it may have a composition of 1.8 ≦ x ≦ 2.2 and 0 < y < 0.1. 〔8〕In the examples of the present invention, in the magnetic refrigeration materials [1] to [5], the hysteresis loss obtained by measuring the M - H loop in the vicinity of the transition temperature T tr is preferably 1 J / kg or less. 〔9〕In the examples of the present invention, the magnetic refrigeration device may use the above magnetic refrigeration materials [1] to [8]. 〔10〕In the examples of the present invention, the magnetic refrigeration device [9] may be for hydrogen liquefaction or for helium liquefaction.

Advantages of the Invention

[0013] According to the magnetic refrigeration material of the present invention, Gd 5-y Dy y Sn x Ge 4-x: A magnetic refrigeration material having a composition of 1.6 < x < 2.4 and 0 < y < 1.1, and Gd5Ge 4-x-z Sn x Si z : By using a magnetic refrigeration material having a composition of 1.6 < x < 2.4 and 0 < z < 1.3, within the temperature range of 40K - 170K near the liquid nitrogen temperature, under a magnetic field of 5T, a giant magnetocaloric effect (MCE) with a magnetic entropy change ΔSm of 17 [J / (kg·K)] or more, more preferably 20 [J / (kg·K)] or more, and a second-order magnetic phase transition (SOMT) material are compatible. Therefore, it is suitable for use in, for example, hydrogen gas liquefaction.

Brief Description of the Drawings

[0014] [Figure 1] An explanatory diagram of the magnetic properties of the Gd5Ge4 compound showing a comparative example of the present invention. (a) is the M - T curve measured at 2T, (b) is the magnetic entropy change in the magnetic field change from 2T to 5T, and (c) is the allotrope plot of the Gd5Ge4 compound. [Diagram 2] An explanatory diagram of the magnetic properties of the Gd5Ge4 - based compound showing a comparative example of the present invention. (a) is a measurement example of the M - T curve at 2T for Gd5Ge3.5M0.5, and (b) is a measurement example of the M - T curve at 2T for the Gd5RE0.5Ge4 compound. [Diagram 3] A measurement example of the M - T curve at 2T for the Gd5(GeSn)4 compound. [Figure 4] The M - H loop of the Gd5Ge4 - based compound showing a comparative example of the present invention measured at the transition temperature. [Diagram 5] A measurement example of the change in magnetic entropy measured at 2T and 5T for Gd5Ge4, which is a comparative example of the present invention, and the Gd5Ge2Sn2 compound showing an example of an embodiment. [Figure 6] The M - T curve measured at 2T for the Gd5Ge2Sn2 - based compound showing an example of an embodiment of the present invention. [Figure 7] A drawing showing the M - H loop of the Gd5Ge2Sn2 - based compound measured at its transition temperature. [Figure 8] A drawing showing the magnetic entropy change of the Gd5Ge2Sn2 - based compound showing an example of an embodiment of the present invention with respect to the magnetic field change from 2T to 5T. [Figure 9] This is an example of measurement of the magnetic entropy change under a 5 T magnetic field for the most studied material in gas liquefaction at cryogenic temperatures, Gd5Ge2Sn2 compound. [Figure 10] FIG. 2 is a schematic diagram illustrating each step of a magnetic refrigeration cycle in which a magnetic refrigeration material is used in an embodiment of the present invention. [Figure 11] FIG. 1 is a schematic diagram illustrating an active regenerative magnetic refrigeration (AMR) cycle. [Figure 12] FIG. 1 is a schematic diagram showing an example of an AMR in which magnetic refrigeration materials are arranged in a cascade configuration, where (A) is a schematic diagram of the device, and (B) is an explanatory diagram of the operating temperature range of the magnetic refrigeration materials. [Figure 13] FIG. 1 is a diagram illustrating a magnetic refrigeration device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The best mode for carrying out the present invention will now be described in detail. <Comparative example of ternary system> As the third element to be added to the Gd5Ge4-based compound, Yb, Ho, and Mg were considered as the third element RE to be added to Gd, and Co, Si, Ni, Sn, Fe, V, Mn, and Cu were considered as the third element M to be added to Ge. Gd, Yb, and Ho can be obtained from Nippon Yttrium Co., Ltd. (Omuta City, Fukuoka Prefecture), and the material is in the form of a block with a purity of 99.9%. Mg, Ge, Si, Fe, and Mn can be obtained from Kojundo Kagaku Kenkyusho Co., Ltd. (Sakado City, Saitama Prefecture), and the material is in the form of a granule with a purity of 99.99%, while Si is 99.999% and Mn is 99.9%. Co can be obtained from Rare Metallic Co., Ltd. (Chiyoda Ward, Tokyo), and the material is in the form of a granule with a purity of 99.97%. Ni, Sn, V, and Cu can be obtained from Furuuchi Chemical Co., Ltd. (Shinagawa, Tokyo) in granular form with a purity of 99.9%. However, Ni is in sheet form.

[0016] The raw materials were lump Gd (purity 99.9%) manufactured by Nippon Yttrium Co., Ltd., lump Ge (purity 99.99%) manufactured by Kojundo Chemical Laboratory, and the above sample was weighed as the third element to obtain Gd5Ge 4-x M x Compounds (where M is Co, Si, Ni, Sn, Fe, V, Mn, or Cu) and Gd 5-y RE y Pure constituent elements of Ge4 compounds (RE is either Yb, Ho, or Mg) were prepared by arc melting the pure constituent elements in an atmosphere-controlled arc furnace manufactured by Nissin Giken Co., Ltd. under an argon atmosphere. 1-7 wt% extra Gd was charged to compensate for the evaporation of Gd. The ingots were homogenized by turning them over and remelting them five times during the arc melting process. The magnetic properties were measured using a SQUID-VSM manufactured by Quantum Design Co., Ltd. Furthermore, polycrystalline samples of Gd5Ge2Sn2-based compounds were also prepared by arc melting the pure constituent elements in an argon atmosphere in a Nissin Giken atmosphere-controlled arc furnace. To compensate for the evaporation of Gd, 1-7 wt% of extra Gd was added. The ingots were homogenized by turning them over and remelting them five times during the arc melting process. The magnetic properties were measured using a SQUID-VSM (Quantum Design).

[0017] Tables 1 and 2 show the composition elements of Gd5Ge4-based compounds with added third elements. 3.5 M 0.5 The composition (at.%) of the compound is shown (M is Co, Si, Ni, Sn, Fe, V, Mn, or Cu) (sample numbers 1-5 and 9-12). However, for Sn, Gd5Ge 4-x Sn x The composition ratio is varied from x=0.5, 1, 2, and 3 (sample numbers 5-8). 4.5 RE 0.5 The composition (at.%) of Ge4 compound is shown (RE is either Yb, Ho, or Mg) (sample numbers 1, 13-15). [Table 1]

[0018] [Table 2]

[0019] FIG. 1 is an explanatory diagram of the magnetic properties of the Gd5Ge4 compound, which is a comparative example of the present invention. (a) is the MT curve measured at 2 T, (b) is the magnetic entropy change in the magnetic field change between 2 T and 5 T, and (c) is the Arrott plot of the Gd5Ge4 compound. The vertical axis of FIG. 1(a) is the magnetization M (Am 2 / kg), the horizontal axis is temperature in K, and an external magnetic field of 2 T is applied as μ0H. In Fig. 1(b), the vertical axis is the magnetic entropy change △Sm [J / (kg K)], the horizontal axis is the temperature in K, and an external magnetic field μ0H of 2 T and 5 T is applied. In the case of 2 T, the maximum magnetic entropy change obtained is 13-14 [J / (kg K)] in the range of 25-38 K. In the case of 5 T, the maximum magnetic entropy change obtained is 24-26 [J / (kg K)] in the range of 48-44 K. The vertical axis of Fig. 1(c) is the magnetization M 2 (Am 2 / kg) 2 The horizontal axis is the external magnetic field μH and the magnetization M(Am 2 / kg) divided by μH / M(T kg / Am 2 )K, with allocation plots at 3K intervals from 6K to 81K. In Figure 1, the magnetic properties of the Gd5Ge4 compound show a typical first-order phase transition, which leads to a huge magnetocaloric effect. 2 A plot of the magnetization versus the ratio of applied magnetic field to magnetization at a fixed temperature (or temperatures) provides a convenient way to determine the presence of ferromagnetic order in a material.

[0020] Table 3 shows the Gd5Ge 3.5 M 0.5 The magnetic properties of the compound are shown (M is Co, Si, Ni, Sn, Fe, V, Mn, or Cu) (sample numbers 1-5, 9-12). However, for Sn,4-x Sn x The composition ratio is varied from x=0.5, 1, 2, and 3 (sample numbers 5-8). 4.5 RE 0.5 The magnetic properties of Ge4 compounds are shown (RE is either Yb, Ho, or Mg) (samples Nos. 1, 13-15). Regarding the Curie temperature Tc (K), Gd5Ge4 (sample number 1) is 38 K at 2 T. The other magnetocaloric effect materials (magnetic refrigeration materials) of sample numbers 2-15 are as shown in the respective columns of Tables 3 and 4. The rate of change of magnetization M per temperature dM / dT(Am 2 / kg·K) is 22.1 for Gd5Ge4 (sample number 1). For magnetocaloric effect materials, the rate of change of magnetization M per temperature dM / dT(Am 2 / kg·K), is preferably 10 or more, more preferably 12 or more, and even more preferably 15 or more. 2 / kg·K) is 10 or more. 3.5 S 0.5 (Sample No. 3) 19, Gd5Ge 3.5 Sn 0.5 (sample number 5) is 12.9, Gd5Ge3Sn1 (sample number 6) is 19.6, and Gd5Ge2Sn2 (sample number 7) is 14. 3.5 Co 0.5 (Sample No. 2) 5, Gd5Ge 3.5 Ni 0.5 (Sample No. 4) 4, Gd5Ge1Sn3 (Sample No. 8) 1.37, Gd5Ge 3.5 Fe 0.5 (Sample No. 9) 3.5, Gd5Ge 3.5 V 0.5 (Sample No. 10) 3.37, Gd5Ge 3.5 Mn 0.5 (Sample No. 11) 5, Gd5Ge 3.5 Cu 0.5 (Sample No. 12) 2.54 is Gd 4.5 Yb 0.5 Ge4 (sample number 13) 5, Gd 4.5 Ho 0.5Ge4 (sample no. 14) 0.5, Gd 4.5 Mg 0.5 The 5 in Ge4 (sample number 15) is not sufficient.

[0021] Figures 2(a) and (b) show the magnetic hysteresis of Gd5Ge4-based compounds in which Ge is replaced by M (see Table 1) and Gd is replaced by rare earth elements (see Table 2). The vertical axis of Figures 2(a) and (b) shows the magnetization M (Am 2 / kg), the horizontal axis is temperature in K, and an external magnetic field of 2 T is applied as μ0H. Thermal hysteresis △T hys Regarding (K), it tends to appear in the first-order magnetic phase transition but not in the second-order magnetic phase transition. In Gd5Ge4 (sample number 1), the thermal hysteresis ΔT hys (K) appears in the range of 4K. For magnetocaloric effect materials, thermal hysteresis △T hys (K) is preferably 5K or less, more preferably 3K or less, and even more preferably 2K or less. Thermal hysteresis △T hys An example of a measurement below 5K (K) is Gd5Ge 3.5 S 0.5 (Sample No. 3) 5K, Gd5Ge2Sn2 (Sample No. 7) <1, Gd5Ge1Sn3 (Sample No. 8) 0K, Gd5Ge 3.5 V 0.5 (Sample No. 10) 5K, Gd5Ge 3.5 Mn 0.5 (Sample No. 11) 2K, Gd5Ge 3.5 Cu 0.5 (Sample No. 12) 5K, Gd 4.5 Yb 0.5 Ge4 (sample number 13) 4K, Gd 4.5 Ho 0.5 Ge4 (sample number 14) 0K, Gd 4.5 Mg 0.5 The 4K content of Ge4 (sample number 15) is sufficient. On the other hand, Gd5Ge 3.5 Co 0.5 (Sample No. 2) 6K, Gd5Ge 3.5 Ni 0.5 (Sample No. 4) 9K, Gd5Ge 3.5 Sn 0.5(Sample No. 5) 13K, Gd5Ge3Sn1 (Sample No. 6) 10K, and Gd5Ge2Sn2 (Sample No. 7) 14K are insufficient.

[0022] Magnetization M(Am 2 / kg) for Gd5Ge4 (sample number 1) is 22.1 at a temperature of 5 K and a magnetic field of 2 T. 2 / kg) is preferably 100 or more, more preferably 120 or more, and even more preferably 150 or more. Magnetization M(Am 2 / kg) is 100 or more, for example, Gd5Ge 3.5 Co 0.5 (Sample No. 2) 103, Gd5Ge 3.5 S 0.5 (Sample No. 3) 190, Gd5Ge 3.5 Ni 0.5 (Sample No. 4) 151, Gd5Ge 3.5 Sn 0.5 (Sample No. 5) 150, Gd5Ge3Sn1 (Sample No. 6) 165, Gd5Ge2Sn2 (Sample No. 7) 185, Gd5Ge 3.5 Fe 0.5 (Sample No. 9) 105, Gd5Ge 3.5 V 0.5 (Sample No. 10) 105, Gd5Ge 3.5 Mn 0.5 (Sample No. 11) 130, Gd 4.5 Yb 0.5 Ge4 (sample number 13) 110, Gd 4.5 Mg 0.5 Ge4 (sample number 15) is sufficient at 120. On the other hand, Gd 4.5 Ho 0.5 0.5 for Ge4 (sample number 14), 83 for Gd5Ge1Sn3 (sample number 8), Gd5Ge 3.5 Cu 0.5 (Sample No. 12) 83, Gd 4.5 Ho 0.5 The 40 in Ge4 (sample number 14) is insufficient.

[0023] Regarding the distinction between first-order magnetic phase transition (FOMT) and second-order magnetic phase transition (SOMT) materials, Gd5Ge1Sn3 (sample number 8) and Gd 4.5 Ho 0.5 Ge4 (sample number 14) was a second-order magnetic phase transition (SOMT) material. Gd5Ge2Sn2 (sample number 7) showed properties that were on the border between first-order magnetic phase transition (FOMT) and second-order magnetic phase transition (SOMT) materials. The remaining samples 1-6, 9-13, and 15 were first-order magnetic phase transition (FOMT) materials.

[0024] The change in magnetic entropy, △S [J / (kg·K)], was measured at 0-5 T and was 25 [J / (kg·K)] for Gd5Ge4 (sample number 1). Another sample for which the change in magnetic entropy, △S [J / (kg·K)], was measured was Gd5Ge 3.5 S 0.5 (sample number 3) is 40, Gd5Ge3Sn1 (sample number 6) is 28, and Gd5Ge2Sn2 (sample number 7) is 32. That is, as can be seen from Tables 3 and 4, when searching for a third element M to be added to a Gd5Ge4-based compound that eliminates hysteresis without lowering the MCE (|△Sm|), 4-x M x Among the third elements M of the compound, it was found that the optimal element was Sn (M is any of Co, Si, Ni, Sn, Fe, V, Mn, or Cu). The other third elements M except Sn (M is any of Co, Ni, Fe, V, Mn, or Cu) and Gd 5-y RE y The third element RE in the Ge4 compound (RE is either Yb, Ho, or Mg) exhibits a rate of change of magnetization M per temperature dM / dT(Am 2 / kg·K) is 10 or more, thermal hysteresis △T hys (K) is 5K or less, or magnetization M(Am 2 / kg) was 100 or more.

[0025] [Table 3]

Table 4

[0026] Figure 3 shows the M-T curve including the heating branch and the cooling branch measured in a magnetic field of 2T for Gd5Ge 4-x Sn x -based compounds (sample numbers 5-8). The vertical axis in Figure 3 is magnetization M (A m 2 / kg), and the horizontal axis is temperature K. As x increases from 0 to 1, the thermal hysteresis increases from 4K to 10K, and the transition temperature rises from 38K to 49K. When x increases to 2, the thermal hysteresis disappears, and the transition temperature rises to 78K. When x increases to 2.2, there is no thermal hysteresis, and the transition temperature rises to 82K. When x increases to 2.4, there is no thermal hysteresis, and the transition temperature rises to 85K, but the magnetization decreases significantly. Further, when x increases to 3, the transition temperature rises to 94K, and due to the antiferromagnetism of Gd5Ge1Sn3, the transition is blunted and the magnetization decreases significantly. Figure 3 shows that the hysteresis can be eliminated by substituting Ge with Sn in an appropriate ratio. Here, focusing on the composition of Gd5Ge 4-x Sn x : 1 ≦ x ≦ 3, the transition temperature can be adjusted from, for example, 38K to 94K. Particularly preferably, 1.6 < x < 2.4, and most preferably, 2.0 ≦ x ≦ 2.3. When x is 1.6 or less, the transition temperature becomes 69K, and the thermal hysteresis is estimated to be about 4K, which is the same level as Gd5Ge4 and is not preferable. When x is 2.4 or more, the transition temperature becomes 85K, and there is no thermal hysteresis, but the decrease in magnetization is significant, which is not preferable.

[0027] Gd5Ge 4-x Sn xIn the magnetic refrigeration material with a composition of 1≦x≦3, the transition temperature without hysteresis extends from 38 K to 94 K, and considering that liquid nitrogen is available in large quantities at a relatively low cost, it has been demonstrated that a magnetic material suitable for use in the temperature range from liquid hydrogen to liquid nitrogen can be obtained. Furthermore, the hysteresis near the transition temperature of the magnetic refrigeration material is qualitatively evaluated by measuring the MH loop at the transition temperature. The hysteresis loop of the magnetic refrigeration material near the transition temperature is measured using a magnetic property measurement system, model MPMSR3, manufactured by Quantum Design, Inc., USA, and sold by Quantum Design, Inc. of Japan. The hysteresis loop of the magnetic refrigeration material is measured under an external magnetization of 2 T, and then the temperature is changed at 2 K / min, and another hysteresis loop is measured.

[0028] FIG. 4 shows the MH loops of Gd5Ge4-based compounds as comparative examples of the present invention, measured at the transition temperature. (a) shows Gd5Ge4, and (b) shows Gd5Ge2Sn2. The vertical axis shows the magnetization M (Am 2 / kg), and the horizontal axis is the magnetic flux density μ0H(T). In Figure 4(a), MH loops for Gd5Ge4 were measured at 3K intervals from 6K to 81K. The hysteresis loss energy is evaluated from the maximum opening of the loop near the transition temperature. For example, for the Gd5Ge4 compound shown in Figure 4(a), the measured value at 45K is the maximum shaded area, and the hysteresis loss is measured to be 80J / kg. In Fig. 4(b), MH loops for Gd5Ge4Sn2 were measured at 3 K intervals from 51 K to 108 K. For the Gd5Ge2Sn2 compound shown in Fig. 4(b), the measured value at 81 K is the maximum shaded area, and is significantly reduced to 8 J / kg. That is, the Gd5Ge2Sn2 compound realizes a hysteresis loss that is one order of magnitude smaller than that of the Gd5Ge4 compound.

[0029] Figure 5 shows the change in magnetic entropy measured for Gd5Ge4 and Gd5Ge2Sn2 based compounds at 2 T and 5 T. The vertical axis of Figure 5 is the magnetic entropy change △Sm [J / (kg·K)], the horizontal axis is the temperature K, and 2 T and 5 T are applied as the external magnetic field μ0H. For Gd5Ge4 (sample number 1), when measured at 2 T, the magnetic entropy change |△Sm| is approximately 15 [J / (kg K)], and the temperature at which the magnetic entropy change peaks is 18 K. When measured at 5 T, the magnetic entropy change |△Sm| is approximately 28 [J / (kg K)], and the temperature at which the magnetic entropy change peaks is 38 K. For the Gd5Ge2Sn2 compound (sample number 7), when measured at 2 T, the magnetic entropy change |△Sm| is approximately 24 [J / (kg K)], and the temperature at which the magnetic entropy change peaks is 75 K. When measured at 5 T, the magnetic entropy change |△Sm| is approximately 32 [J / (kg K)], and the temperature at which the magnetic entropy change peaks is 78 to 82 K.

[0030] <Example of quaternary system> Next, it will be explained that the transition temperature can be adjusted by adding a fourth element to the Gd5Ge2Sn2 compound as a starting material. As the fourth element to be added to the Gd5Ge2Sn2 compound, Tb, Dy, Er, Ho, and La were considered as the fourth element RE to be added to Gd (sample numbers 28-36), and Si was considered as the fourth element to be added to Ge (sample numbers 37-41). Tb, Dy, Er, Ho, and La can be obtained from Japan Yttrium Co., Ltd. (Omuta City, Fukuoka Prefecture), and the material is in the form of a block with a purity of 99.9%. Si can be obtained from High Pure Chemical Research Institute Co., Ltd. (Sakado City, Saitama Prefecture), and the material is in the form of a granule with a purity of 99.999%.

[0031] The raw materials were lump Gd (purity 99.9%) manufactured by Nippon Yttrium Co., Ltd., lump Ge (purity 99.99%) manufactured by Kojundo Chemical Laboratory, and granular Sn (purity 99.9%) manufactured by Furuuchi Chemical Co., Ltd. (Shinagawa-ku, Tokyo). The above samples were weighed as the fourth element, and the mixture was determined to be Gd5Sn2Ge. 2-x S x Compound and Gd 5-y RE y Pure constituent elements of Ge2Sn2 compounds (RE is Tb, Dy, Er, Ho, or La) were prepared by arc melting the pure constituent elements in an atmosphere-controlled arc furnace manufactured by Nissin Giken Co., Ltd. under an argon atmosphere. 1-7 wt% extra Gd was charged to compensate for the evaporation of Gd. The ingots were homogenized by turning them over and remelting them five times during the arc melting process. The magnetic properties were measured using a SQUID-VSM manufactured by Quantum Design Co., Ltd. Similarly, polycrystalline samples of Gd5Ge2Sn2-based compounds (sample numbers 21-27) were prepared by arc melting the pure constituent elements in an argon atmosphere in an atmosphere-controlled arc furnace manufactured by Nissin Giken Co., Ltd. In order to compensate for the evaporation of Gd, 1-7 wt% of extra Gd was charged. The ingots were homogenized by turning them over five times during the arc melting process and remelting them. The magnetic properties were measured using a SQUID-VSM (manufactured by Quantum Design Co., Ltd.).

[0032] Table 5 shows the Gd5Ge 4-x Sn x Compounds based on Gd (sample numbers 21-27) 5-y RE y Ge2Sn2-based compounds (RE is Tb, Dy, Er, Ho, or La) (sample numbers 28-36), and Gd5Sn2Ge 2-z S z The composition (at.%) of the compounds (sample numbers 37-41) is shown. In addition, Gd5Ge 4-x Sn x In the notation of Gd5Sn based compounds, Tables 5 and 6 x Ge 4-x In some cases, the order of Ge and Sn is reversed, but this is for tabulation purposes and has no other meaning. Gd 5-y REy Ge2Sn2-based compounds and Gd5Sn2Ge 2-z S z Similarly, in the notation of Gd-based compounds, Tables 5 and 6 5-y RE y Sn x Ge 4-x As shown above, the order of Ge and Sn is reversed, but this is for tabulation purposes only and there is no other intention. [Table 5]

[0033] FIG. 6 is a MT curve measured at 2 T for a Gd5Ge2Sn2-based compound according to an embodiment of the present invention. The vertical axis shows the magnetization M (Am 2 / kg), the horizontal axis is temperature in K, and an external magnetic field of 2 T is applied. 2-z S z By the Si substitution of Gd, the transition temperature can be increased from 80 K to 170 K while maintaining the hysteresis-free state of those transitions, covering the liquefaction temperatures of nitrogen, oxygen, and natural gas (samples no. 37-39, 22(8)). Furthermore, by the rare earth substitution of Gd (RE is Dy), the transition temperature can be decreased to 40 K (see Table 6, samples no. 31, 32). That is, by focusing on the fourth element added to the Gd5Ge2Sn2 compound and appropriately adjusting the type and amount of the fourth element, the transition temperature can be adjusted from 40K to 170K. Thus, a wide operating temperature window for the Gd5Ge2Sn2-based compound can be realized, and a magnetic refrigeration material having the properties desired for application to the liquefaction of various types of gases can be provided. That is, according to the magnetic refrigeration material of the present invention, it is possible to select a magnetic refrigeration material with an appropriate composition according to the set temperature range of each stage of magnetic refrigeration, which is applied to the liquefaction of various types of gases such as hydrogen, nitrogen, oxygen, and natural gas, and has a transition temperature without hysteresis from 40K to 170K and a band temperature width of about 20K to 30K.

[0034] Table 6 shows the Gd5Ge 4-x Sn x Compounds based on Gd (sample numbers 21-27) 5-y REy Ge2Sn2-based compounds (RE is any one of Tb, Dy, Er, Ho, or La) (sample numbers 28 - 36), and Gd5Sn2Ge 2-z Si z -based compounds (sample numbers 37 - 41) are shown for their magnetic properties (at.%).

Table 6

[0035] When Si (silicon) is selected as the fourth element, the following composition formula: Gd5Ge 4-x-z Sn x Si z : A magnetocaloric effect material with a composition of 1.6 < x < 2.4 and 0 < z < 1.3 can be obtained. By selecting the composition ratio within the range of 1.6 < x < 2.4 for Sn (tin) and 0 < z < 1.3 for Si (silicon), the transition temperature T tr of the magnetic phase transition is in the temperature range of 80K to 170K, and a magnetocaloric effect material that exhibits a second-order magnetic phase transition within a range of 20K before and after the transition temperature T tr or shows the characteristics of the boundary region between the second-order magnetic phase transition and the first-order magnetic phase transition can be obtained. The magnetic entropy change △S can reach 17 [J / (kg·K)] or more under a 5T magnetic field. Note that when performing a linear approximation of the magnetic entropy change △S from the measured values in Table 6 (sample numbers 24, 37 - 41), the composition for which the magnetic entropy change △S can reach 20 [J / (kg·K)] or more under a 5T magnetic field is Gd5Ge 4-x-z Sn x Si z : 1.6 < x < 2.4 and 0 < z < 1.1. The composition for which the magnetic entropy change △S can reach 25 [J / (kg·K)] or more under a 5T magnetic field is Gd5Ge 4-x-z Sn x Si z : 1.6 < x < 2.4 and 0 < z < 0.9. The composition for which the magnetic entropy change △S can reach 30 [J / (kg·K)] or more under a 5T magnetic field is Gd5Ge 4-x-z Sn x Si z : 1.6 < x < 2.4 and 0 < z ≤ 0.4.

[0036] As the fourth element, when Dy (dysprosium) is selected, the following composition formula: Gd 5-y Dy y Sn x Ge 4-x : A magnetocaloric effect material having a composition of 1.6 < x < 2.4 and 0 < y < 1.1 can be obtained. By selecting the composition ratio within the range of 1.6 < x < 2.4 for Sn (tin) and 0 < y < 1.1 for Dy (dysprosium), the transition temperature T tr of the magnetic phase transition is in the temperature range of 35 K to 75 K, and a magnetocaloric effect material that exhibits a second-order magnetic phase transition within a range of 20 K before and after the transition temperature T tr or shows the characteristics of the boundary region between the second-order magnetic phase transition and the first-order magnetic phase transition can be obtained. Preferably, when x = 2.0 for Sn (tin), the following composition formula: Gd 5-y Dy y Sn2Ge2: A magnetocaloric effect material having a composition of 0 < y < 1.1 can be obtained. In addition, when performing a linear approximation of the magnetic entropy change ΔS from the measured values in Table 6 (sample numbers 24, 31 - 33), the composition for which the magnetic entropy change ΔS is 20 [J / (kg·K)] or more under a 5 T magnetic field is Gd 5-y Dy y Sn x Ge 4-x : 1.6 < x < 2.4 and 0 < y < 0.8. The composition for which the magnetic entropy change ΔS is 25 [J / (kg·K)] or more under a 5 T magnetic field is Gd 5-y Dy y Sn x Ge 4-x : 1.8 ≤ x ≤ 2.2 and 0 < y < 0.4. The composition for which the magnetic entropy change ΔS is 30 [J / (kg·K)] or more under a 5 T magnetic field is Gd 5-y Dy y Sn x Ge 4-x : 1.8 ≤ x ≤ 2.2 and 0 < y < 0.1.

[0037] Furthermore, the hysteresis of a magnetic refrigeration material is qualitatively evaluated by measuring its MH loop at its transition temperature, where the hysteresis loss energy is evaluated by the maximum opening of the loop near the transition temperature. Figure 7 shows the MH loops of Gd5Ge2Sn2-based compounds measured at their transition temperatures. Figure 7(a) shows the Gd5Ge2Sn2 compound, and Figure 7(b) shows the Gd5Sn2Ge 0.8 S 1.2 In Fig. 7(c), the MH loops for the compound Gd4Dy1Sn2Ge2 are plotted. In Fig. 7, the vertical axis is the magnetization M(Am 2 / kg), and the horizontal axis is the magnetic flux density μ0H(T). In the Gd5Ge4 compound (sample number 1), the hysteresis loss was measured to be 80 J / kg, as shown in Figure 4(a). In contrast, in the Gd5Ge2Sn2 compounds (sample numbers 7 and 24), the hysteresis loss was significantly reduced to 8 J / kg, as shown in Figure 7(a). In Figure 7(a), the MH loop of Gd5Ge2Sn2 was measured at 3 K intervals from 51 K to 108 K, and the hysteresis loss ΔE hys That is, the Gd5Ge2Sn2 compound has achieved a hysteresis loss that is one order of magnitude smaller than that of the Gd5Ge4 compound. In Fig. 7(b), Gd5Sn2Ge 0.8 S 1.2 For the compound (sample number 39), the MH loop was measured at 3 K intervals from 150 K to 189 K, and the hysteresis loss ΔE hys In Fig. 7(c), the MH loop of Gd4Dy1Sn2Ge2 (sample number 32) was measured at 3K intervals from 27K to 60K, and the hysteresis loss ΔE hys We are looking for Gd5Sn2Ge 0.8 S 1.2 and hysteresis loss ΔE of Gd4Dy1Sn2Ge2 hys is 0 J / kg, indicating that there is no hysteresis loss.

[0038] Figure 8 is a graph showing the magnetic entropy change with respect to magnetic field changes of 2 T and 5 T for a Gd5Ge2Sn2-based compound according to one embodiment of the present invention, with the vertical axis representing the magnetic entropy change △Sm [J / (kg·K)] and the horizontal axis representing temperature K. Figure 8 and Table 6 summarize the magnetic entropy change with magnetic field changes of 2 T and 5 T for Gd5Ge2Sn2-based compounds. Usually, the reduction of hysteresis is achieved at the expense of magnetic entropy change. Here, by substituting Sn for Ge, we achieved both an order of magnitude smaller hysteresis loss and a larger magnetic entropy change. Specifically, |△Sm| under a 5 T magnetic field increase from 25 [J / (kg·K)] (Gd5Ge4·sample no. 1) to 32 [J / (kg·K)] (Gd5Ge2Sn2·sample no. 24(7)), and the hysteresis loss decreased from 80 J / kg (Gd5Ge4·sample no. 1) to 8 J / kg (Gd5Ge2Sn2·sample no. 24(7)).

[0039] As shown in Figure 8 and Table 6, Gd 5-y Dy y In the Sn2Ge2 compound, where y = 1 (sample number 31), a transition temperature of 41 K can be achieved and there is no thermal hysteresis, making it a desirable property for hydrogen liquefaction using an active magnetic regeneration (AMR) system. When Ge is replaced by Si, Gd5Sn2Ge 0.8 S 1.2 For compound (sample number 39), |△Sm| is 17.9 [J / (kg K)] at 170 K, and the hysteresis loss gradually becomes zero. On the other hand, when Gd is replaced with Dy, the Gd4Dy1Sn2Ge2 compound (sample number 32) shows that the transition temperature decreases from 78 K to 40 K while maintaining zero hysteresis loss and |△Sm| of 17.6 [J / (kg K)] at 40 K in hydrogen liquefaction applications using AMR.

[0040] In addition, Gd5Ge 4-x Sn x For sample numbers 25-27 of the A system compounds, the rate of change of magnetization M per temperature dM / dT(Am 2 / kg·K) is Gd5Ge 2.4 Sn1.6 Since it was lower than (sample number 23), the magnetic entropy change |ΔSm| under a magnetic field change of 5 T was not measured. Gd 5-y Tb y Ge 4-x Sn x For (sample numbers 28 - 30), the magnetic entropy change |ΔSm| under a 5 T magnetic field was not measured within the temperature range of 20 K to 85 K from near liquid hydrogen temperature to near liquid nitrogen temperature. Gd 5-y RE y Ge 4-x Sn x For (RE is any one of Er, Ho, or La) (sample numbers 34 - 36), within the temperature range of 20 K to 85 K from near liquid hydrogen temperature to near liquid nitrogen temperature, under a 5 T magnetic field, since the value of the rate of change of magnetization M with respect to temperature dM / dT (Am 2 / kg·K) was less than 1, the magnetization M (Am 2 / kg) and the magnetic entropy change |ΔSm| under a magnetic field change of 5 T were not measured. Gd5Sn2Ge 2-z Si z For the Si - based compounds (sample numbers 37 - 41), since the Curie temperature T c was in the temperature range of 102 K to 195 K and higher than liquid nitrogen temperature, the magnetization M under a 5 T magnetic field was not measured within the temperature range of 20 K to 85 K from near liquid hydrogen temperature to near liquid nitrogen temperature.

[0041] Subsequently, in the Gd 5-y RE y Ge2Sn2 - based compounds, when any one of Tb, Dy, Er, Ho, or La is selected as the fourth element RE, the following composition formula: Gd 5-y RE y Ge 4-x Sn x : A magnetic refrigeration material having a composition of 1.6 < x < 2.4, 0.0 < y < 1.5 can be obtained. For this magnetic refrigeration material, for Tb, the Curie temperature T c is in the temperature range of 35 K to 85 K, and the said Curie temperature Tc The magnetic phase transition is either secondary or 30 K around the Curie temperature T c is a temperature range from 35K to 85K, and the Curie temperature T c It shows a second-order magnetic phase transition in the range of 30 K around the first-order magnetic phase transition, or shows characteristics in the boundary region between the second-order and first-order magnetic phase transitions. In addition, this magnetic refrigeration material has a Curie temperature T c is within the temperature range of 35K to 85K and satisfies at least one of the following three conditions under a 5T magnetic field. (i) The rate of change of magnetization M per temperature dM / dT(Am 2 / kg·K) is 17 to 50. (ii) Thermal hysteresis △T hys (K) is between 0K and 3K, or (iii) Magnetization M(Am 2 / kg) is between 100 and 200.

[0042] Here, under a 5T magnetic field, the thermal hysteresis △T hys The composition formula of a magnetic refrigeration material that satisfies the requirement of 3K or less for (K) is as follows: Gd 5-y RE y Ge 4-x Sn x (RE is Tb, Dy, Er, Ho, or La): 1.6 <x<2.4、0.0<y<1.5 In addition, under a 5T magnetic field, the magnetization M(Am 2 The composition formula of the magnetic refrigeration material in which the content of MnO2 in the magnetic refrigeration material is 100 or more and 200 or less is as follows: Gd 5-y RE y Ge 4-x Sn x (RE=Tb or Dy): 1.6 <x<2.4、0.0<y<1.5

[0043] In Fig. 9, the non-hysteretic magnetocaloric properties of different compounds for gas liquefaction applications at cryogenic temperatures are summarized, with the vertical axis representing the magnetic entropy change △Sm [J / (kg K)] and the horizontal axis representing the temperature K. At temperatures below 30K, there are many options for magnetic refrigerant materials, for example, HoB2, ErAl2, HoN, and HoNi2, which show sufficient entropy change (|△Sm| of 20 [J / (kg K)] or more). However, there are few magnetic materials that show |△Sm| of 20 [J / (kg K)] or more at temperatures between 60 and 150K. Here, the Gd5Ge2Sn2-based compound conceived in the present invention shows a huge MCE of |△Sm| of 17 [J / (kg·K)] or more, more preferably 20 [J / (kg·K)] or more, which can cover a wide operating temperature window of 40 K to 170 K for liquefying multiple types of gases such as hydrogen, nitrogen, oxygen, and natural gas.

[0044] The magnetic refrigeration material of the present invention exhibits a significantly larger magnetic entropy change than existing non-hysteretic transition materials. For example, Gd 4.5 Dy 0.5 The magnetic entropy change of Sn2Ge2 was |△Sm| of 25 [J / (kg K)] (sample number 31), which is 140% larger than that of DyAl2 in hydrogen liquefaction using AMR at the same temperature of 60 K. On the other hand, the Gd5Sn2Ge2 compound showed |△Sm|=32 [J / (kg K)], which is 184% larger than that of the Dy-Fe-Si compound for nitrogen liquefaction (77 K), and Gd5Sn2Ge 1.6 S 0.4 The compound showed |△Sm| = 30.9 [J / (kg K)], which is 177% higher than that of the Tb-Fe-Si compound in natural gas liquefaction (sample number 37). 1.2 S 0.8The compound's |△Sm| is 26 [J / (kg·K)], which is 240% larger than that of (Gd,Tb)Al2 at the same temperature (sample number 38). From the above comparison, it is clearly shown that the magnetic refrigeration material of the present invention is significantly superior to existing magnetic refrigeration materials in terms of its huge MCE and tunable transition temperature in liquefying various gases at cryogenic temperatures.

[0045] In summary, we have demonstrated that the trade-off between large MCE and small hysteresis can be overcome by appropriately selecting the type and composition ratio of the third and fourth elements in the conventional first-order phase transition (FOMT) material Gd5Ge4 compound. By substituting the third element Sn with Ge in an appropriate ratio, we can simultaneously improve the MCE and minimize the hysteresis. Furthermore, by selecting Dy or Si as the fourth element, it was demonstrated that the transition temperature could be adjusted from 40 K by substituting Dy for Gd and up to 170 K by substituting Si for Ge while maintaining a hysteresis-free transition.

[0046] Next, a magnetic refrigeration device in which the magnetic refrigeration material of the present invention is used will be described. FIG. 10 is a schematic diagram illustrating each step of the magnetic refrigeration cycle. In the magnetic refrigeration cycle, a thermal cycle similar to the vapor compression cycle is formed by a repeated cycle of entropy change (temperature increase) due to excitation in a constant temperature environment and adiabatic temperature change (temperature decrease) due to demagnetization in an adiabatic state.

[0047] Fig. 11 is a schematic diagram for explaining an active regenerative magnetic refrigeration (AMR) cycle. In Fig. 11, the dashed line indicates the temperature distribution before the process operation, and the solid line indicates the temperature distribution after the process operation. The magnetic refrigerator for the AMR cycle consists of an AMR bed, which doubles as a magnetic refrigeration material packed bed and a heat exchanger, a magnet, a drive unit (displacer), and a heat transfer medium (hydrogen, helium, air, etc.). The drive unit is a control device that adjusts the relative positions of the magnetic refrigeration material and the AMR bed.

[0048] The AMR cycle consists of four steps: adiabatic excitation, movement of the heat transfer medium (movement from the low temperature end to the high temperature end), adiabatic demagnetization, and movement of the heat transfer medium (movement from the high temperature end to the low temperature end). (1) In adiabatic excitation, the magnetic refrigeration material is excited, and the temperature of the entire AMR bed increases. (2) When transferring heat from the low temperature end to the high temperature end, the heat transfer medium is moved to the high temperature side by a driving device. The high temperature heat transfer medium in the AMR bed is transferred to the high temperature side, while the inflow of heat transfer medium from the low temperature side changes the temperature distribution in the AMR bed. (3) In adiabatic demagnetization, the temperature in the AMR bed decreases due to the magnetocaloric effect. The temperature decreases overall while maintaining a temperature distribution in the AMR bed. (4) When transferring heat from the high temperature end to the low temperature end, the heat transfer medium is moved to the low temperature side by a driving device. The low temperature heat transfer medium in the AMR bed is transferred to the low temperature side, while the inflow of the heat transfer medium from the high temperature side changes the temperature distribution in the AMR bed.

[0049] If these four steps are considered as one cycle, after one cycle, the temperature distribution in the AMR bed will be slightly lower on the low-temperature side than at the start of the cycle, and slightly higher on the high-temperature side than at the start of the cycle. By repeating this heat storage and regeneration cycle, the temperature difference will increase, and eventually the temperature distribution in the AMR bed will become almost constant. The temperature distribution in the AMR bed is determined by the properties of the magnetic refrigeration material that makes up the AMR bed.

[0050] FIG. 12 is a schematic diagram showing an example of an AMR in which magnetic refrigeration materials are arranged in a cascade arrangement, where (A) is a schematic diagram of the device and (B) is an explanatory diagram of the operating temperature range of the magnetic refrigeration materials. In the AMR shown in Figure 12, by selectively arranging magnetic refrigeration materials with different operating temperature ranges, it is possible to realize an AMR mechanism with a hierarchical structure that efficiently generates a temperature difference by magnetization and demagnetization. Curie temperature T C is the temperature at which a ferromagnetic material exhibits paramagnetism and corresponds to the temperature at which the maximum magnetocaloric effect occurs. Therefore, in the AMR shown in Figure 12, multiple temperature zones (T C1 ~T C4), a large magnetocaloric effect is observed, so performance degradation is unlikely to occur even if a temperature gradient is generated in the magnetic refrigeration material packed bed. C By selectively arranging magnetic refrigeration materials having this property, it is possible to realize an AMR suitable for hydrogen liquefaction.

[0051] FIG. 13 is a schematic diagram showing the main part of a magnetic refrigeration device. A magnetic refrigeration material including the material of the embodiment described above can be used. One form of this magnetic refrigeration material may be particles having a particle diameter in the range of 50 μm to 1000 μm. For example, the particle diameter may be 50 μm or more, 100 μm or more, or 200 μm or more, or 2000 μm or less, 1000 μm or less, or 500 μm or less, in a spherical approximation. In addition, a predetermined range may be set by appropriately combining these lower and upper limits. By adopting a particle form, the filling rate in the AMR bed can be increased, and the heat exchange cross-sectional area and pressure loss with the heat transport refrigerant can be changed depending on the particle diameter. The smaller the particle diameter, the larger the heat exchange cross-sectional area, which is effective in improving the refrigeration performance from this point of view, but on the other hand, the smaller the particle diameter, the higher the pressure loss, which reduces the refrigeration performance. The actual pressure loss depends not only on the particle diameter but also on the type of heat transport refrigerant and the operating conditions. Here, the particle diameter is determined by the volume-based median diameter (d 50 ) and the volume-based average particle size can be measured, for example, by a microtrack or laser scattering method. More specifically, static image analysis and dynamic image analysis can be used. In the former, a large number of particle images (SEM images, etc.) are taken, and the particle diameter converted into a circle can be calculated from the area of ​​each particle using image analysis software.

[0052] A magnetic refrigeration device 200 equipped with such a magnetic refrigeration material can be used to generate ultra-low temperatures, for example, to liquefy hydrogen. The magnetic refrigeration device 200 further includes an AMR bed 220 filled with a magnetic refrigeration material 210, a magnetic field application means 230 for applying a magnetic field to the AMR bed 220, a cooling stage 290 for cooling an object to be cooled by applying cold and hot, and a heat exchanger 240 for discharging heat generated by the magnetic refrigeration work in the AMR bed 220. The magnetic field application means 230 can be any means for applying a magnetic field to the AMR bed 220, and it is practical to use a magnetic field with a strength of about 1 to 10 T (tesla), for example. A superconducting magnet, a permanent magnet, or the like can be adopted as the magnetic field application means 230. In addition, the relative positions of the magnetic field application means 230 and the AMR bed 220 can be changed by a driving mechanism (not shown) to change the magnitude of the magnetic field applied to the AMR bed 220.

[0053] A pre-cooling stage 260 is provided on the high temperature side of the AMR bed 220, and an 80K shield 270 is connected to the low temperature side of the pre-cooling stage 260, and a 300K shield 280 is connected to the high temperature side of the pre-cooling stage 260. Furthermore, a cooling stage 290 is provided on the low temperature side of the AMR bed 220, and a liquefying vessel 250 is provided and thermally connected to the cooling stage 290. That is, gas to be cooled is supplied to the liquefying vessel 250 and liquefied. In addition, an inlet and outlet for the heat transport refrigerant are provided in the AMR bed 220, and the heat transport refrigerant can flow back and forth inside the AMR bed 220 through the gaps in the magnetic refrigeration material 210.

[0054] The liquefaction vessel 250 is supplied with a gas 310 (e.g., hydrogen, helium (He), etc.) to be liquefied from a tank (not shown). The magnetic refrigeration device 200 may be operated as follows. A magnetic field is applied to the AMR bed 220 filled with the magnetic refrigeration material 210 by the magnetic field application means 230 to raise the temperature of the magnetic refrigeration material 210. Next, the heat transport refrigerant is caused to flow in a direction 300A from the low-temperature end side to the high-temperature end side of the AMR bed 220. The heat transport refrigerant exchanges heat with the magnetic refrigeration material 210 filled inside the AMR bed 220 and receives hot heat, while flowing through the gaps in the magnetic refrigeration material 210 and flowing out from the high-temperature end of the AMR bed 220. The heat transport refrigerant flowing out from the high-temperature end of the AMR bed 220 flows into the heat exchanger 240 that exhausts hot heat via the pre-cooling stage 260, and excess heat is exhausted to the outside. Next, the magnetic field in which the magnetic refrigeration material 210 is filled is removed (reduced), causing the temperature of the magnetic refrigeration material 210 to drop.

[0055] The heat transport refrigerant is then caused to flow in a direction 300B from the high temperature end side to the low temperature end side of the AMR bed 220. The heat transport refrigerant flows into the high temperature end of the AMR bed 220 via the pre-cooling stage 260, and while being cooled by heat exchange with the magnetic refrigeration material 210 filled inside, flows through the gaps in the magnetic refrigeration material 210, and reaches the low temperature end of the AMR bed 220. The flow of the heat transport refrigerant is driven by a refrigerant driving means (not shown). The refrigerant driving means is not particularly limited as long as it can drive an oscillating flow that reciprocates the heat transport refrigerant in synchronization with the AMR cycle, and examples of the refrigerant driving means include a system that combines a piston, a blower and a valve.

[0056] When the temperature of the low-temperature end of the AMR bed 220 drops below the boiling point of liquid hydrogen (20K at atmospheric pressure), the hydrogen gas supplied to the liquefaction vessel 250 is cooled and concentrated / liquefied by heat exchange with the cooling stage 290 provided on the low-temperature end side of the AMR bed 220. By repeating this process, the gas inside the liquefaction vessel 250 is periodically liquefied or cooled. [Industrial Applicability]

[0057] As described above in detail, the Gd 5-y Dy y Sn x Ge 4-x Compounds based on Gd5Ge 4-x-z Sn x S z According to the compound, Gd5Ge 4-x Sn x By appropriately adjusting the type and amount of the fourth element added to the system compound, it is possible to realize a giant and reversible MCE that is 140-240% larger than that of existing materials in a wide temperature window (40K-170K), making it suitable for use in the liquefaction of various types of gases, including hydrogen, nitrogen, oxygen, and natural gas. [Explanation of symbols]

[0058] 200 Magnetic Refrigeration Device 220 AMR Bed 230 Magnetic field application means 240 Heat exchanger 250 Liquefaction vessel 260 Pre-cooling stage 270 80K Shield 280 300K Shield 290 Cooling Stage 300A Heat transport refrigerant flow direction 300B Heat transport refrigerant flow direction

Claims

1. It consists of Gd (gadolinium), Ge (germanium), Sn (tin), Si (silicon), and unavoidable impurities. The following chemical formula: Gd ５ Ge ４－ｘ－ｚ Sn ｘ Si ｚ A magnetic refrigeration material having a composition of 1.6 < x < 2.4 and 0 < z < 1.

3.

2. In the magnetic refrigeration material according to claim 1, Magnetic phase transition transition temperature T ｔｒ The temperature range is from 80K to 170K. The transition temperature T ｔｒ A magnetic refrigeration material characterized by exhibiting a secondary magnetic phase transition in a range of 20K before and after a certain temperature, or exhibiting characteristics of the boundary region between a secondary magnetic phase transition and a primary magnetic phase transition.

3. It consists of Gd (gadolinium), Dy (dysprosium), Ge (germanium), Sn (tin), and unavoidable impurities. The following chemical formula: Gd ５－ｙ Dy ｙ Sn ｘ Ge ４－ｘ : A material for magnetic refrigeration having a composition of 1.6 < x < 2.4 and 0 < y < 1.

1.

4. In the magnetic refrigeration material according to claim 3, Gd ５－ｙ Dy ｙ Sn ２ Ge ２ A magnetic refrigeration material having a composition of 0 < y < 1.

1.

5. In the magnetic refrigeration material according to claim 3, Magnetic phase transition transition temperature T ｔｒ The temperature range is from 35K to 75K. The transition temperature T ｔｒ A magnetic refrigeration material characterized by exhibiting a secondary magnetic phase transition in a range of 20K before and after a certain temperature, or exhibiting characteristics of the boundary region between a secondary magnetic phase transition and a primary magnetic phase transition.

6. In the magnetic refrigeration material according to claim 1, The transition temperature T ｔｒ A magnetic refrigeration material characterized in that, within a range of 20K before and after a certain point, the magnetic entropy change is 17 [J / (kg·K)] or more under a 5T magnetic field.

7. In the magnetic refrigeration material according to claim 6, A magnetic refrigeration material characterized by achieving a magnetic entropy change of 20 [J / (kg·K)] or more under a 5T magnetic field.

8. In the magnetic refrigeration material according to claim 2, The transition temperature T ｔｒ A magnetic refrigeration material characterized by having a hysteresis loss of 1 J / kg or less, obtained by measuring the M-H loop in the vicinity.

9. In the magnetic refrigeration material according to claim 3, A magnetic refrigeration material characterized in that, within a range of 20 K before and after the transition temperature T tr, the magnetic entropy change is 17 [J / (kg·K)] or more under a 5 T magnetic field.

10. In the magnetic refrigeration material according to claim 9, A magnetic refrigeration material characterized by achieving a magnetic entropy change of 20 [J / (kg·K)] or more under a 5T magnetic field.

11. In the magnetic refrigeration material according to claim 5, A magnetic refrigeration material characterized in that the hysteresis loss obtained by measuring the M-H loop near the transition temperature T tr is 1 J / kg or less.

12. A magnetic refrigeration apparatus using the magnetic refrigeration material described in claims 1 to 11.

13. The magnetic refrigeration apparatus according to claim 12, wherein the magnetic refrigeration apparatus is for hydrogen liquefaction or helium liquefaction.

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