2013 Volume 54 Issue 3 Pages 363-366
High specific heats of the magnetic regenerative material, at the temperatures lower than 20 K, is crucial for a regenerative cryocooler to reach a liquid-helium temperature. The hydrogenation of the magnetic regenerative materials ErNi and ErNi2 may change their structures, magnetic properties and specific heats, which will be investigated in this paper. XRD patterns show that crystalline and amorphous phases can both be formed in the hydrogenation at 293 K. The insertion of hydrogen atoms can lead to a larger specific heat, measured by a physical property measurement system (PPMS), in some higher temperature ranges. But the peak values of specific heat of the hydrides are lower than those of their parent compounds below 15 K, which indicates that the idea of regenerative material hydrogenation should be left out in the efforts of regenerator performance enhancement.