ErAg蓄冷材料に及ぼすAl, Fe, Pd添加効果

抄録

We have measured the low temperature specific heats for Er (Ag_1-xM_x) (M=Al, Pd and Fe, x≤0.2) alloys over the temperature range of 1.5-25K to explore efficient regenerator materials suitable at low temperatures around 10K. In particular, the peak height of the volumetric specific heat of Er (Ag_0.9Al_0.1) alloy has reached 1.2J/(Kcm³) at 16.5K, which is 1.5 times higher than that of the ErAg compound previously reported. Its large specific heat is attributed to the 4-fold degeneracy in the ground state of the Er 4f-levels. Moreover, we have revealed that the addition of third elements M=Pd and Fe to the ErAg compound could lower the peak position of the specific heat to about 10K. We conclude that a series of the ternary Er (Ag_1-xM_x) (M=Al, Pd and Fe, x≤0.2) alloys can serve as good regenerator materials in the temperature range below 17K.