Metal-insulator transition and itinerant antiferromagnetism in NiS2-xSex pyrite

The bandwidth-controlled metal-insulator (MI) transition in pyrite-type NiS2-xSex has been investigated. The results indicate that the approach to the MI transition from the metallic side is profoundly affected by the presence of the antiferromagnetic metal (AFM) phase (0.4 < x < 1.0) immediately next to the MI phase boundary. In the paramagnetic metal (PM) phase (1.0 < x less than or equal to 2.0), the approach is simply characterized by mass enhancement. In the AFM phase, however, the approach is driven by a marked decrease in the carrier density on approaching the insulating phase.