磁性Sb化合物の蓄冷材応用  [in Japanese] Application of Magnetic Sb Compounds as Regenerative Materials  [in Japanese]

In order to obtain high regenerative effectiveness, the heat capacity of the regenerator materials must be larger than that of helium, which is used as the working gas. For a magnetic regenerator material to be effective in the low temperature range, its transition temperature must be within the range in which the helium regenerative operation is performed. Materials with different heat capacities are arranged in multi-layers in a regenerator to obtain higher regenerative efficiency. The relactive effectiveness of multi-layer regenerators for liquefied helium was analyzed by computer simulation and experimental results. New materials, including heavy rare-earth and antimony (Sb) compounds, were used as the magnetic regenerator materials. Antimony compounds have especially sharp single-phase transitions in the low temperature range. In this study, the central results were the measured heat capacities of HoSb and DySb, which are anti-ferromagnetic materials with large spin values in the low temperature range. The relation between refrigeration capacity and regenerative effectiveness was investigated when these multi-layer regenerative materials were packed into the second stage of a Gifford-McMahon cycle cryorefrigerator.