Magnetism of the Fe$^{2+}$ and Ce$^{3+}$ sublattices in Ce$_{2}$O$_{2}$FeSe$_{2}$: a combined neutron powder diffraction, inelastic neutron scattering and density functional study

TL;DR

This study combines experimental neutron scattering and density functional theory to analyze the magnetic interactions in Ce$_{2}$O$_{2}$FeSe$_{2}$, revealing ferromagnetic Fe--Se interactions and weak correlations in the Fe--Se sheets, relevant to understanding iron-based superconductivity.

Contribution

It provides a comprehensive combined experimental and theoretical analysis of magnetic interactions in Ce$_{2}$O$_{2}$FeSe$_{2}$, highlighting ferromagnetic Fe--Se interactions and weak correlations in the Fe--Se sheets.

Findings

Ferromagnetic nearest-neighbor Fe--Se interactions confirmed.

Weak correlations in Fe--Se sheets indicated by DFT.

Fe on-site repulsion similar to other iron-based superconductors.

Abstract

The discovery of superconductivity in the 122 iron selenide materials above 30 K necessitates an understanding of the underlying magnetic interactions. We present a combined experimental and theoretical investigation of magnetic and semiconducting Ce$_{2}$O$_{2}$FeSe$_{2}$ composed of chains of edge-linked iron selenide tetrahedra. The combined neutron diffraction and inelastic scattering study and density functional calculations confirm the ferromagnetic nature of nearest-neighbour Fe -- Se -- Fe interactions in the ZrCuSiAs-related iron oxyselenide Ce$_{2}$O$_{2}$FeSe$_{2}$. Inelastic measurements provide an estimate of the strength of nearest-neighbor Fe -- Fe and Fe -- Ce interactions. These are consistent with density functional theory calculations, which reveal that correlations in the Fe--Se sheets of Ce$_{2}$O$_{2}$FeSe$_{2}$ are weak. The Fe on-site repulsion $U_{Fe}$ is comparable to that reported for oxyarsenides and K$_{1-x}$Fe$_{2-y}$Se$_{2}$, which are parents to iron-based superconductors.