Large orbital magnetic moment and Coulomb correlation effects in FeBr2

Abstract

We have performed an all-electron fully relativistic density-functional calculation to study the magnetic properties of FeBr2. We show that the correlation effect enhances the contribution from orbital degrees of freedom of d electrons to the total magnetic moment on Fe2+, as opposed to the common notion of a nearly total quenching of the orbital moment on the Fe2+ site. The insulating nature of the system is correctly predicted when the Hubbard parameter U is included. Energy bands around the gap are very narrow in width, and originate from the localized Fe-3d orbitals, which indicates that FeBr2 is a typical example of a Mott insulator.