"Covalent magnetism" and invar-like behavior within ternary nitrides: An ab initio study

Abstract

Magnetic properties and bonding analyses of perovskite structure-derived TFe3N (T = Ru, Os) nitrides have been investigated within density functional theory using both pseudo potential and all electron methods. At equilibrium, spin degenerate non-magnetic (NM) and ferromagnetic (FM) calculations of energy versus volume show that the ground state of the two compounds is ferromagnetic. Magnetic moments of Ru/Os and Fe, respectively, being situated at two different crystallographic sites are studied over a wide range of the cubic lattice parameter. The volume expansion indicates that iron atoms show itinerant magnetism while Ru and Os exhibit a localized behavior. Important magnetovolume effects are observed, with saturation of the magnetic moment reached in RuFe3N but not in OsFe3N. The electronic structure is visualized for the different binding characters Fe-N versus Ru/Os-N with the help of electron localization plots. The density of states of the ferromagnetic ground state is interpreted on the basis of a covalent magnetic model which goes beyond the Stoner rigid band model. An Invar-like behavior is predicted for the two nitrides. © 2007 Verlag der Zeitschrift für Naturforschung,.