Orbital selective local moment formation in iron: first principle route to an effective model

We revisit a problem of theoretical description of alpha-iron. By performing LDA+DMFT calculations in the paramagnetic phase we find that Coulomb interaction and, in particular Hund exchange, yields the formation of local moments in e_g 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 e_g 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 e_g electrons 2p=1.04 mu_B. The effective bosonic model, which allows to describe magnetic properties of iron near the magnetic phase transition, is proposed.