Experimental and computational investigation of structure and magnetism in pyrite Co1-xFexS2: Chemical bonding and half-metallicity

Abstract

Bulk samples of the pyrite chalcogenide solid solutions Co1?xFexS2 s0?x?0.5d, have been prepared and their crystal structures and magnetic properties studied by x-ray diffraction and SQUID magnetization measurements. Across the solution series, the distance between sulfur atoms in the persulfide sS2 2?d unit remains nearly constant. First principles electronic structure calculations using experimental crystal structures as inputs point to the importance of this constant S-S distance, in helping antibonding S-S levels pin the Fermi energy. In contrast hypothetical rock-salt CoS is not a good half metal, despite being nearly isostructural and isoelectronic. We use our understanding of the Co1?xFexS2 system to make some prescriptions for new half-metallic ferromagnetic.