CaIrO3 post-perovskite, a j = 1/2 quasi-one-dimensional antiferromagnet

TL;DR

This study uses advanced calculations to reveal that CaIrO3 is a j=1/2 quasi-one-dimensional antiferromagnet with strong c-axis superexchange interactions, serving as an analogue for Earth's mantle post-perovskite.

Contribution

The paper provides detailed theoretical insights into the magnetic interactions and chemical bonding in CaIrO3, predicting large antiferromagnetic superexchange and its quasi-one-dimensional magnetic nature.

Findings

CaIrO3 exhibits a 120 meV antiferromagnetic superexchange along the c axis.

CaIrO3 has significantly weaker ferromagnetic couplings along the a axis.

The magnetic structure is consistent with a stripy antiferromagnetic order.

Abstract

The 5d5 iridate CaIrO3 is isostructural with the post-perovskite phase of MgSiO3, recently shown to occur under extreme pressure in the lower Earth's mantle. It therefore serves as an analogue of post-perovskite MgSiO3 for a wide variety of measurements at ambient conditions or achievable with conventional multianvile pressure modules. By multireference configuration-interaction calculations we here provide essential information on the chemical bonding and magnetic interactions in CaIrO3. We predict a large antiferromagnetic superexchange of 120 meV along the c axis, the same size with the interactions in the cuprate superconductors, and ferromagnetic couplings smaller by an order of magnitude along a. CaIrO3 can thus be regarded as a j = 1/2 quasi-one-dimensional antiferromagnet. While this qualitatively agrees with the stripy magnetic structure proposed by resonant x-ray diffraction, the detailed microscopic picture emerging from our study, in particular, the highly uneven admixture of t2g components, provides a clear prediction for resonant inelastic x-ray scattering experiments.