Microscopic Magnetic Properties of Co (S_<i>x</i>Se_1-<i>x</i>)₂ –⁵⁹Co NMR–

Abstract

59 Co spin-echo NMR were carried out for metallic compounds Co(S x Se 1- x ) 2 with pyrite structure over the entire composition range to investigate the microscopic magnetic properties of this system. From the results obtained, it is concluded that the character of Co atoms is unique in each composition with \(0 \leq x \lesssim 0.6\), whereas above about x =0.86 two kinds of Co atoms coexist, one is non-magnetic and the other is ferromagnetic with 0.85 µ B . It is also shown that the effect of electron correlations on the magnetism increases with increasing sulphur content. The characteristic field-induced metamagnetic transition around x =0.88 is concluded to be due to the progressive-discontinuous transition from the nonmagnetic state to the ferromagnetic state with increasing external magnetic field. Discussions on the mechanism of the coexistence of nonmagnetic and ferromagnetic Co atoms and the composition dependence of the fraction of the ferromagnetic Co atoms are briefly given.