SPIN, CHARGE, AND BONDING IN TRANSITION-METAL MONO-SILICIDES

We review some of the relevant physical properties of the transition m etal mono-silicides with the FeSi structure (CrSi, MnSi, FeSi. CoSi, N iSi, etc.) and explore the relation between their structural character istics and the electronic properties. We confirm the suggestion orgina lly made by Pauling that the FeSi structure supports two quasi-atomic d-states at the transition metal atom. This shell contains from 0 to 4 electrons in the sequence CrSi to NiSi. In FeSi the two quasi-atomic d-electrons are responsible for the high temperature S = 1 state, whic h is compensated for T = 0 by two itinerant electrons associated with the Fe-Si resonance bonds. Published by Elsevier Science B.V.