SPECIFIC-HEAT OF A REGENERATOR MATERIAL ER3NI

Specific heat measurement was performed in the temperature range from 800 mK to 62 K on the regenerator material Er3Ni which is an antiferro magnet with a Neel temperature of 6.1 K and possesses a large volumetr ic heat capacity even at temperatures above T(N). The magnetic contrib ution to the specific heat has been carefully divided into two parts, one of which is caused by entropy change due to the magnetic ordering and the other a contribution from higher energy level states (Schottky anomaly). The energy levels of the 4f electrons for Er3+ were calcula ted using the point-charge model, and compared with the experimental d ata. The entropy change of the Schottky anomaly is large compared with that of magnetic ordering and important for the regenerator material.