Nonlocal correlations in the vicinity of the $\alpha$-$\gamma$ phase transition in iron within a DMFT plus spin-fermion model approach

TL;DR

This paper investigates nonlocal correlations near the iron $ ext{-}eta$ phase transition using a combined DMFT and spin-fermion model, revealing their impact on phase energies and transition temperatures.

Contribution

It introduces a novel approach combining DMFT with a spin-fermion model to accurately capture nonlocal correlations in iron near the phase transition.

Findings

Nonlocal corrections lower the Curie temperature of the $ ext{α}$ phase.

Nonlocal effects are crucial for energy proximity of $ ext{α}$ and $ ext{γ}$ phases.

The approach improves agreement with experimental transition temperatures.

Abstract

We consider nonlocal correlations in iron in the vicinity of the $\alpha$-$\gamma$ phase transition within the spin-rotationally-invariant dynamical mean-field theory (DMFT) approach, combined with the recently proposed spin-fermion model of iron. The obtained nonlocal corrections to DMFT yield a decrease of the Curie temperature of the $\alpha$ phase, leading to an agreement with its experimental value. We show that the corresponding nonlocal corrections to the energy of the $\alpha$ phase are crucially important to obtain the proximity of energies of $\alpha$ and $\gamma$ phases in the vicinity of the iron $\alpha$-$\gamma$ transformation.