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

TL;DR

This paper uses first-principles calculations to show that Hund exchange interactions induce local moments in the e_g electron band of alpha-iron, leading to an effective model for magnetic properties.

Contribution

It introduces an orbital-selective approach to modeling iron's magnetic behavior based on LDA+DMFT calculations and local moment formation.

Findings

Hund exchange causes local moments in e_g electrons

e_g electrons exhibit non-Fermi-liquid behavior

Effective local moment of 1.04 μ_B for e_g electrons

Abstract

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.