Electronic correlations in FeAl : an LDA+DMFT study

Abstract

We apply the local density approximation combined with dynamical mean-field theory (LDA+DMFT) to the intermetallic compound FeAl. This LDA+DMFT study is motivated by the fact that FeAl shows unexpected magnetic properties: experimentally it is known to be paramagnetic while conventional spin-polarized LDA calculations yield a ferromagnetic ground state. This discrepancy between theory and experiment can be explained by the presence of narrow Fe d bands at the Fermi level, which require a more accurate treatment of electronic correlations beyond LDA.<br />The low energy part of the LDA Hamiltonian is projected onto a set of 9 maximally localized Wannier orbitals: 5 Fe d and 4 Al sp3 orbitals.<br />These orbitals are then treated within DMFT, whereby local interactions are applied only to the Fe d orbitals, while we allow for electron hopping and charge transfer also with the Al sp3 orbitals. The Kanamori interaction parameters are computed ab initio, by using the constrained random-phase approximation approach (cRPA). A continuous-time quantum Monte Carlo algorithm in its hybridization expansion is used for the solution of the impurity problem.<br />We find that FeAl is an intermediately correlated metal with a quasiparticle weight of Z =0.8. In agreement with experimental results, the material does not show any tendency to long-range magnetic order.<br />