Magnetic Collapse and the Behavior of Transition Metal Oxides at High Pressure

TL;DR

This study uses advanced theoretical methods to analyze how transition metal oxides transition from insulators to metals under high pressure, revealing a link between electronic structure changes and magnetic collapse.

Contribution

It provides a comprehensive theoretical analysis of pressure-induced electronic and magnetic transitions in transition metal oxides using DFT+DMFT methods.

Findings

Mott insulator-metal transition occurs under pressure in MnO, FeO, CoO, NiO.

Magnetic moments collapse during the transition, linked to electronic changes.

Transition pressures decrease from MnO to CoO, but NiO requires much higher pressure.

Abstract

We report a detail theoretical study of the electronic structure and phase stability of transition metal oxides MnO, FeO, CoO, and NiO in their paramagnetic cubic B1 structure by employing dynamical mean-field theory of correlated electrons combined with \emph{ab initio} band structure methods (DFT+DMFT). Our calculations reveal that under pressure these materials exhibit a Mott insulator-metal transition (IMT) which is accompanied by a simultaneous collapse of local magnetic moments and lattice volume, implying a complex interplay between chemical bonding and electronic correlations. Moreover, our results for the transition pressure show a monotonous decrease from ~ 145 GPa to 40 GPa, upon moving from MnO to CoO. In contrast to that, in NiO, magnetic collapse is found to occur at remarkably higher pressure of ~ 429 GPa. We provide a unified picture of such a behavior and suggest that it is primary a localized to itinerant moment behavior transition at the IMT that gives rise to magnetic collapse in transition metal oxides.