Thermal Expansion of NiS2, Ni0.9Co0.1S2, Ni0.9Cu0.1S2 and Ni0.95Cu0.05S2

Abstract

The thermal expansion of NiS 2 , Ni 0.9 Co 0.1 S 2 , Ni 0.9 Cu 0.1 S 2 and Ni 0.95 Cu 0.05 S 2 has been measured from 4.2 K to room temperature. The anomalies, which correspond to antiferromagnetic ordering and to appearance of weak ferromagnetism, have been observed in all specimens. The lattice, electronic and magnetic Gruneisen constans are determined. The magnetic Gruneisen constant changes its sign from negative to positive corresponding to the metal-semiconductor transition which occurs between Ni 0.9 Co 0.1 S 2 and Ni 0.93 Co 0.07 S 2 .