Abstract
The low temperature specific heats for a series of the ErxAg100-x (x=40, 50, 60 and 70) alloys have been measured over the temperature range 1.6-30K to evaluate their applicability as a regenerator material. A large magnetic specific heat has been observed for these multi-phase samples. It is found to originate from the 4-fold degeneracy in the ground state of the Er 4f-levels. We also found that, in the temperature range of 10-20K, the volumetric specific heats for the x=50-70 samples exceed that for the Er3Ni compound, which is currently known as one of the most efficient regenerator materials. The x=40 sample is superior to Er3Ni below 6K. In addition, we found that the thermal conductivity for the present Er-Ag alloys is 5-10 times higher than that for the Er3Ni below 25K. We are led to conclude that the present Er-Ag alloys are promising as a regenerator material, particularly when a composition-gradient composite regenerator material, in which the Er concentration is varied from 70 to 40 along the direction of the gas flow, is fabricated.
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