# Momentum-dependent susceptibilities and magnetic exchange in bcc iron from supercell DMFT calculations

## TL;DR

This study combines DFT and DMFT to analyze how magnetic susceptibilities and exchange interactions in paramagnetic bcc iron depend on momentum and temperature, providing detailed orbital-resolved insights.

## Contribution

It introduces a method to relate momentum-dependent susceptibilities to magnetic exchange in Hund's metals using supercell DMFT calculations.

## Key findings

- Orbital-resolved susceptibilities at high-symmetry wave vectors calculated.
- Orbital-resolved exchange interactions extracted and interpolated across the Brillouin zone.
- Temperature dependence of exchange interactions estimated using the spherical model.

## Abstract

We analyze the momentum- and temperature dependences of the magnetic susceptibilities and magnetic exchange interaction in paramagnetic bcc iron by a combination of density functional theory and dynamical mean-field theory (DFT+DMFT). By considering a general derivation of the orbital-resolved effective model for spin degrees of freedom for Hund's metals, we relate momentum-dependent susceptibilities in the paramagnetic phase to the magnetic exchange. We then calculate non-uniform orbital-resolved susceptibilities at high-symmetry wave vectors by constructing appropriate supercells in the DMFT approach. Extracting the irreducible parts of susceptibilities with respect to Hund's exchange interaction, we determine the corresponding orbital-resolved exchange interactions, which are then interpolated to the whole Brillouin zone. Using the spherical model we estimate the temperature dependence of the resulting exchange between local moments.