Correlation between cooling power and heat quantity of Er-Ho binary nitride as regenerator of 4K-GM cryocooler

Abstract

Abstract Advanced regenerator materials of erbium and holmium binary nitrides, Er x Ho1-x N (x = 0 - 1) were studied. Its specific heat vs. temperature curve, possesses a peak due to the magnetic phase transition at their Curie temperature. The cooling power at 4.2 K of a commercial 4K-GM cryocooler filled with the binary nitride of x = 0.625, 0.75, 0.875 or 1 was evaluated. It was found that the cooling power at 4.2 K has a good linear correlation with the heat quantity, which is calculated by integrating C with respect to T in the region of 4.2 - 7.0 K. Three binary nitrides (x = 0.625, 0.875 and 1) filled in series along the regenerator column gave 26% higher cooling power than that filled with HoCu2.