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

在低温领域，氦等冷介质和低温发电技术是非常重要的。对于气体制冷，需要高效的储气罐来产生极低的温度。蓄水器接收卡诺循环产生的热量。铅通常用作蓄水器。在这种情况下，不可能产生低于10K的低温，这阻碍了氦的广泛使用。在本研究中，为了克服上述的柏里尔效应，进行了高效储罐的开发。直到去年，各种具有尽可能大的热容的化合物和合金已经被研究。低温比热测量表明，与应用潜力较大的Er-Ni化合物相比，具有较大磁矩的稀土化合物HoPb2具有较大的热容。然而，由于这种化合物在大气中容易氧化，所以不如储存物好。对具有较大随机磁各向异性的非晶态合金和含稀土元素的准晶进行了低温比热测量。然而，这些材料的热容不是很大，不适合使用蓄电池。从这些结果可以得出结论，提高HoPb2的大气阻力是应用的必要。

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.