Paramagnetism in NiSe₂

Abstract

The magnetic properties of a pyrite compound NiSe₂ have been investigated by the ⁷⁷Se NMR, the magnetic susceptibility and the specific heat measurements in the temperature range between 1.6 and 300 K. The electronic specific heat coefficient, γ, is obtained to be (8.5±1.0) mJ/K²mol. The values of the magnetic susceptibility and the Knight shift are estimated to be 2.17×10⁻⁴ emu/mol and +(1.0±0.1)%, respectively, both being independent of temperature. The product of the nuclear spin-lattice relaxation time and temperature, T₁T, is found to be constant with a value or 240 msec K. From these results, it is concluded that NiSe₂ is one of the typical Pauli paramagnets and the usual Korringa relation holds with a relatively small exchange enhancement effect. Discussions of the origin of the hyperfine coupling constant of ⁷⁷Se are also given in conjunction with the reported result of CoSe₂.