Theoretical investigation of magnetic order in ReOFeAs, Re = Ce, Pr

TL;DR

This study uses density functional theory to analyze the magnetic ground state of ReOFeAs compounds, revealing collinear antiferromagnetic order in Fe and Re sites, and showing that Coulomb interactions turn ReOFeAs into a Mott insulator.

Contribution

It provides a theoretical understanding of magnetic ordering in ReOFeAs, highlighting the role of Coulomb interactions in electronic structure and insulating behavior.

Findings

Fe sites exhibit collinear antiferromagnetic order

Re magnetic moments also order antiferromagnetically

Coulomb interactions induce a Mott insulating state

Abstract

Density functional theory (DFT) calculations are carried out on ReOFeAs, Re = Ce, Pr, the parent compounds of the high-T$_c$ superconductors ReO$_{1-x}$F$_{x}$FeAs, in order to determine the magnetic order of the ground state. It is found that the magnetic moments on the Fe sites adopt a collinear antiferromagnetic order, similar to the case of LaOFeAs. Within the generalized gradient approximation along with Coulomb onsite repulsion (GGA+U), we show that the Re magnetic moments also adopt an antiferromagnetic order for which, within the ReO layer, same spin Re sites lie along a zigzag line perpendicular to the Fe spin stripes. While within GGA the Re 4f band crosses the Fermi level, upon inclusion of onsite Coulomb interaction the 4f band splits and moves away from the Fermi level, making ReOFeAs a Mott insulator.