Low Temperature Properties of HoSb, DySb, and GdSb

Abstract

Materials including rare-earth and Sb compounds were developed as regenerator materials for a 4K GM refrigerator. Sb compounds have a remarkably large peak value of specific heat in the low temperature range. First, the heat capacities, thermal conductivity, and thermal expansion of HoSb, DySb and GdSb, which are anti-ferromagnetic with a large spin value in the low temperature range, were measured. Then, the results of these measurements were used to analyze the problems encountered when Sb compounds were used as the regenerative materials in a GM refrigerator.

As for the thermal expansion, the measured values of Sb compounds were compared with that of fabric-impregnated phenol-formaldehyde resin, which is usually used as the wall material of a regenerator. As regards the thermal conductivity, the thermal diffusivity was obtained by using the measured values of thermal conductivity and specific heat. The heat penetration depth was evaluated from the thermal diffusivity. Discussion of the heat penetration depth is based on the figures obtained in a previous experiment using a GM refrigerator with HoSb packed at the cold end of the second stage of a multi-layer regenerator.