Compensated Half-metallicity in the Trigonally Distorted Perovskite-type NiCrO$_3$

TL;DR

This study uses first principles calculations to demonstrate that NiCrO$_3$ can exhibit a compensated half-metallic state, which is valuable for spintronic applications, and explores how electron correlations and volume changes influence this property.

Contribution

The paper reveals that NiCrO$_3$ can be a compensated half-metallic material under certain conditions, expanding the understanding of half-metallicity in distorted perovskites.

Findings

NiCrO$_3$ is an exactly compensated half-metal within LSDA.

Including Coulomb interactions (U) turns it into an insulator with a narrow spin-up gap.

Volume compression can induce CHM even with correlation effects.

Abstract

Using first principles calculations, we investigate the electronic and magnetic properties of the trigonally distorted (R-3c) perovskite-derived NiCrO$_3$. Within the local spin density approximation (LSDA), our calculations show that this system is an exactly compensated half-metal (CHM). The local spin moments of Cr 2.04, and antialigned Ni -1.41 and three oxygens -0.63 (in the units of $\mu_B$), indicate high spin S=3/2 Cr$^{3+}$ and S=3/2 (NiO$_3$)$^{3-}$ units. Considering reasonable values of the on-site Coulomb repulsion U on both Ni and Cr ions with LDA+U approach, this system becomes an insulator (as reported by Chamberland and Cloud) having a narrow gap in the spin-up channel, whereas the other channel has a large gap of ~3 eV. Although inclusion of U seemingly leads to the transition Ni$^{2+} --> high spin S=3/2 Ni$^{3+}$, consistent with the experimentally observed effective moment, the zero net moment remains unchanged due to either reduction of oxygen local moments or enhancement of Cr local moment. Compression of volume by 10% leads to CHM even when correlation effects are included.These results suggest the possibility of a CHM state in NiCrO$_3$ and provide another route to search for CHM, which is a property sought by many.