Orbital-selective formation of local moments in α -iron: First-principles route to an effective model

We revisit a problem of theoretical description of α-iron. By performing local-density approximation plus dynamical mean-field theory calculations in the paramagnetic phase we find that Coulomb interaction and, in particular, Hund exchange, yields the formation of local moments in eg electron band, which can be traced from imaginary-time dependence of the spin-spin correlation function. This behavior is accompanied by non-Fermi-liquid behavior of eg electrons and suggests using local-moment variables in the effective model of iron. By investigating orbital-selective contributions to the Curie-Weiss law for Hund exchange I=0.9 eV we obtain an effective value of local moment of eg electrons 2p=1.04μB. The effective bosonic model, which allows to describe magnetic properties of iron near the magnetic phase transition, is proposed.