Study on the Development of High Efficient Materials for Generation of Very Low Temperatures

在低温学领域，氦等冷介质和低温生成技术是重要的。对于天然气制冷，需要高效的储层来产生极低的温度。热源接收卡诺循环放出的热量。铅通常被用作储层。在这种情况下，不可能产生低于10 K的低温。这阻碍了氦的广泛使用。为了克服上述障碍，本研究进行了高效储层的开发。直到去年，人们一直在研究各种具有尽可能大的热容量的化合物和合金。低温比热测量表明，具有大磁矩的稀土化合物HoPb_2与具有较高应用潜力的Er-Ni化合物相比，具有较大的热容。然而，由于该化合物在大气中极易氧化，因此不适合作为储层。对具有较大随机磁各向异性的非晶合金和含稀土准晶进行了低温比热测量。然而，这些材料的热容量并没有那么大，不能使用储热器。由此得出结论，提高HoPb_2的耐大气压性能是应用的必要条件。

In the field of cryogenics, cold media such as helium and technics of generation for low temperatures are important. For gas refrigeration, high efficient reservoirs are necessary to generate very low temperatures. The reservoir receives the heat carried out by the Carnot cycle.Pb has conventionally used as a reservoir. In this case, it is impossible to generate low temperatures below 10 K.This prevents using widely helium. In the present study, the development of the high efficient reservoir has been carried out in order to overcome the berrier mentioned above.Until last year, various compounds and alloys with a heat capacity as large as possible have been investigated. It has become clear by low-temperature specific heat measurements that rare earth compound HoPb_2 with a large magnetic moment has a large heat capacity, compared with that of Er-Ni compounds which have high potentials for applications. However, this compound is not so good as the reservoir because of the ready oxidation at atmosphere. The low temperature specific heat measurements for amorphous alloys with a large random magnetic anisotropy and quasicrystals containing rare earth element have been carried out. However, the heat capacity for these materials is not so large to use the reservoir.From these results, it is concluded that the improvement of the atmospheric resistance of HoPb_2 is necessary for application.