Screened moments and absence of ferromagnetism in FeAl

TL;DR

This study uses advanced electronic correlation methods to explain why FeAl remains paramagnetic experimentally, despite predictions of ferromagnetism from standard theories, highlighting the role of quantum fluctuations.

Contribution

The paper demonstrates that incorporating dynamical mean field theory resolves the discrepancy between experimental and theoretical magnetic behavior in FeAl.

Findings

No ferromagnetism observed down to 100 K

Susceptibility decreases at low temperatures

Quantum fluctuations screen local magnetic moments

Abstract

While the stoichiometric intermetallic compound FeAl is found to be paramagnetic in experiment, standard band-theory approaches predict the material to be ferromagnetic. We show that this discrepancy can be overcome by a better treatment of electronic correlations with density functional plus dynamical mean field theory. Our results show no ferromagnetism down to 100 K and since the susceptibility is decreasing at the lowest temperatures studied we also do not expect ferromagnetism at even lower temperatures. This behavior is found to originate from temporal quantum fluctuations that screen short-lived local magnetic moments of 1.6 $\mu_B$ on Fe.