Large Orbital Magnetic Moment in Feo, Fes and Febr2

Magnetic moment of the Fe2+ ion in FeO, FeS and FeBr2 has been calculated within the quantum atomistic solid-state theory to substantially exceed a value of 4 muB in the magnetically-ordered state at 0 K. In all compounds the large orbital moment, of 0.7 - 1.1 muB, has been revealed. Our calculations show that for the meaningful analysis of electronic and magnetic properties of FeO, FeS and FeBr2 the intra-atomic spin-orbit coupling is essentially important and that the orbital moment is largely unquenched in 3d- ion containing compounds.