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Materials research for new magnetic refrigeration using metamagnetic transition

利用变磁转变的新型磁制冷材料研究

基本信息

批准号：
09555185
负责人：
SHIGA Masayuki
金额：
$ 8.06万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

Because of high thermodynamic efficiency, magnetic refligeration has been an attractive technology for the low temperature generation. The search for new materials with a large magnetocaloric effects (MCE) in the temperature range of interest is strongly desired for further improvement of magnetic refrigeration. Some of the intermetallic compounds containing rare earth elements R undergo a first-order-magnetic transition from a ferrimagnetic to paramagnetic state at low temperatures. Above TィイD2cィエD2, these materials exhibit a metamagnetic transition in appropriate magnetic fields, which suggests a large MCE. In this research, we have studied the MCE of ErCoィイD22ィエD2 and DyMnィイD22ィエD2GeィイD22ィエD2. The nature of magnetic transition RcoィイD22ィエD2 and RMnィイD22ィエD2GeィイD22ィエD2 was also studied and discussed.In EiCoィイD22ィエD2, we have found the large MCE in 32-40 K. The maximum height of the isothermal entropy change, ΔS and the adiabatic temperature change, ΔTィイD2adィエD2 in a field change of 0 to 8 T are 12 J/K mol and 13 K,respectively, which are larger than those of other R compounds in the same temperature range. The substitution of 10%Ni for Co lowers Tc from 32 K to 13 K without reduction of the MCE. These results strongly suggest Er(CoィイD21-xィエD2NiィイD2xィエD2)ィイD22ィエD2 has a high potential for working materials of magnetic refrigeration. From the studies on DyMnィイD22ィエD2GeィイD22ィエD2, we have revealed the nature of the MCE of first-order magnetic transition systems. Namely, the maximum values of the MCE are not sensitive to magnetic field, while the temperature range with the large MCE is increased linearly with increasing magnetic field. In other words, the MCE of the first-order magnetic transition systems is large in relatively weak magnetic fields, although it extends over a narrow temperature range. These characteristics are advantageous to the active magnetic regenerative materials.

磁制冷技术由于具有较高的热效率而成为低温发电领域的一项重要技术。为了进一步提高磁制冷的性能，人们迫切需要寻找在感兴趣的温度范围内具有大的磁热效应（MCE）的新材料。一些含有稀土元素R的金属间化合物在低温下经历从亚铁磁到顺磁的一阶磁转变。在T_（10）D_2c_（10）D_2以上，这些材料在适当的磁场中表现出变磁转变，这表明大的MCE。在本研究中，我们研究了ErCo双金属D22双金属D2和DyMn双金属D22双金属D2 Ge双金属D22双金属D2的MCE。对Rco_（22）Ge_在0 ~ 8 T的磁场变化范围内，该化合物的最大等温熵变高度ΔS和最大绝热温变高度ΔT_（12）J/K mol和Δ T_（12）D_（13）K，均大于同温度范围内的其它R化合物。10%Ni取代Co使Tc从32 K降低到13 K，而MCE没有降低。这些结果有力地表明Er（Co_（21-x）Ni_（21-x）D_2Ni_（22-x）D_2Ni_（2通过对DyMn_xD_（22）Ge_xD_（22）Ge_xD_（22）Ge_xD_（22）的研究，揭示了一级磁跃迁系统的MCE性质。也就是说，MCE的最大值对磁场不敏感，而具有大MCE的温度范围随着磁场的增加而线性增加。换句话说，一阶磁转变系统的MCE在相对弱的磁场中很大，尽管它在很窄的温度范围内延伸。这些特性对活性磁蓄冷材料是有利的。