Modelling the electronic structure and magnetic properties of LiFeAs and FeSe using hybrid-exchange density functional theory

TL;DR

This study uses hybrid-exchange density functional theory to analyze the electronic structure and magnetic properties of LiFeAs and FeSe, revealing their magnetic configurations and exchange interactions, consistent with previous experiments.

Contribution

It provides detailed theoretical insights into the magnetic ordering and exchange interactions in LiFeAs and FeSe using hybrid density functional calculations, advancing understanding of their electronic and magnetic behavior.

Findings

Spin-2 configuration has lower energy in both materials.

LiFeAs favors checkerboard antiferromagnetic order; FeSe favors stripe order.

Next nearest neighbour exchange interactions are larger, suggesting collinear ground state.

Abstract

The electronic structure and magnetic properties of LiFeAs and FeSe have been studied using hybrid exchange density functional theory. The total energies for a unit cell in LiFeAs and FeSe with different spin states including non-magnetic and spin-2 are calculated. The spin-2 configuration has the lower energy for both LiFeAs and FeSe. The computed anti-ferromagnetic exchange interactions between spins on the nearest (next nearest) neighbouring Fe atoms in LiFeAs and FeSe are approximately 14 (17) meV and 6 (13) meV respectively. The total energies of the checkerboard and stripe-type anti-ferromagnetic ordering for LiFeAs and FeSe are compared, yielding that for LiFeAs the checkerboard is lower whereas for FeSe the stripe-type is lower. However, owing to the fact that the exchange interaction of the next nearest neighbour is larger than that of the nearest one, which means that the collinear ordering might be the ground state. These results are in agreement with previous theoretical calculations and experiments. Especially the calculations for LiFeAs indicate a co-existence of conducting d-bands at the Fermi surface and d-orbital magnetism far below the Fermi surface. The theoretical results presented here might be useful for the experimentalists working on the electronic structure and magnetism of iron-based superconductors.