Rotationally-Invariant Exchange Interaction: The Case of Paramagnetic Iron

TL;DR

This paper extends spin-fluctuation theory to include full rotational invariance of exchange interactions using LDA+DMFT, accurately predicting magnetic properties of paramagnetic iron.

Contribution

It introduces a generalized approach for treating rotationally-invariant exchange interactions within LDA+DMFT, improving magnetic property predictions.

Findings

Curie temperature matches experimental data

Ising-type exchange overestimates Curie temperature

Method captures spin-density fluctuations effectively

Abstract

We present a generalization of the spin-fluctuation theory of magnetism which allows us to treat the full rotational invariance of the exchange interaction. The approach is formulated in terms of the local density approximation plus dynamical mean-field theory (LDA+DMFT), providing a systematic many-body treatment of the effect of spin-density fluctuations. This technique is employed to study the electronic and magnetic properties of paramagnetic $\alpha$ iron. Our result for the Curie temperature is in good agreement with experiment, while the calculations with the Ising-type exchange interaction yield almost twice overestimated value.