The metal–non-metal transition in nickel sulphide (NiS)

Abstract

Hexagonal nickel sulphide shows a transition at 260 K from an antiferromagnetic to a paramagnetic state which is accompanied by an abrupt change in the conductivity. It is suggested that this is not a Néel temperature, that is a destruction of long-range order, but a first-order disappearance of the moments, and that it occurs because of the screening out of the Hubbard intra-atomic electron-electron interaction by the electrons in the sulphur 3p band. It is also shown that the low temperature phase is probably a semimetal.