Study of the volume and spin collapse in orthoferrite LuFeO_3 using LDA+U

TL;DR

This study uses ab initio LDA+U calculations to analyze the volume and spin collapse in LuFeO_3, revealing a pressure-induced phase transition and emphasizing the importance of accurately determining correlation parameters.

Contribution

It demonstrates the necessity of including strong correlation effects via LDA+U to accurately describe phase transitions in LuFeO_3 and explores the dependence on U and J parameters.

Findings

Identified a 6% volume discontinuity at 50 GPa transition

Showed a linear relationship between transition pressure and U/J parameters

Revealed a significant reduction in Fe magnetic moments during transition

Abstract

Rare earth (R) orthoferrites RFeO_3 exhibit large volume transitions associated with a spin collapse. We present here ab initio calculations on LuFeO_3. We show that taking into account the strong correlation among the Fe-3d electrons is necessary. Indeed, with the LDA+U method in the Projector Augmented Wave (PAW), we are able to describe the isostructural phase transition at 50 GPa, as well as a volume discontinuity of 6.0% at the transition and the considerable reduction of the magnetic moment on the Fe ions. We further investigate the effect of the variation of U and J and find a linear dependence of the transition pressure on these parameters. We give an interpretation for the non-intuitive effect of J. This emphasizes the need for a correct determination of these parameters especially when the LDA+U is applied to systems (e.g in geophysical investigations) where the transition pressure is a priori unknown.