Multipole Orders in a Chain Ferrate Na2FeSe

TL;DR

This paper classifies magnetic Fe multipole orders in Na2FeSe, analyzing their symmetry, magnetoelectric properties, and diffraction patterns, highlighting the role of axial and polar multipoles in the electronic structure.

Contribution

It introduces a symmetry-based classification of Fe multipole orders in Na2FeSe and predicts their diffraction signatures, advancing understanding of magnetic multipoles in correlated electron systems.

Findings

Identification of fundamental and staggered multipole orders

Calculated diffraction patterns show multipole contributions

Fe ions exhibit enantiomorphic symmetry affecting electronic structure

Abstract

Fundamental block and staggered orders of magnetic Fe multipoles in Na2FeSe2 are classified by their symmetry and magnetoelectric properties. Our structure model incorporates ferromagnetic or antiferromagnetic coupling between chains. The ferrate salt is valued in studies of highly correlated electrons as the only iron selenide known to possess chain-like structural units hosting ferrous cations. Axial and polar (Dirac) multipoles are compulsory in the electronic structure since Fe ions exhibit enantiomorphic symmetry in the parent K2ZnO2-type compound. Calculated Bragg diffraction patterns for neutrons and x-rays reveal specific contributions from both multipole types.