Magnetic refrigeration down to 0.2 K by heavy fermion metal YbCu4Ni.

Ytterbium-based heavy-fermion metals have recently attracted attention as magnetic refrigeration materials generating low-temperature environments below 1 K without using expensive 3 He. YbCu 4 Ni is known to exhibit a giant value of specific heat divided by temperature C / T ∼ 7.5 J / K 2 mol below 0.2 K, implying high potential of magnetic refrigeration. In this paper, we report magnetic refrigeration down to 0.2 K from the initial temperatures of 1.8 K by YbCu 4 Ni ingots installed in a commercial 4 He refrigerator. The performance is consistent with that evaluated by our DC magnetization and specific heat measurements. Our study demonstrates the high performance of YbCu 4 Ni without precious metals as a magnetic refrigeration material with moderately high density of Yb atoms (∼ 0.02 Yb mol / cm 3) and high thermal conductivity. [ABSTRACT FROM AUTHOR]