First-principles study of the electronic structure and magnetism of CaIrO$_3$

TL;DR

This study uses first-principles calculations to explore the electronic structure and magnetism of CaIrO$_3$, revealing that spin-orbit coupling and Coulomb interactions induce a Mott insulating state with specific magnetic ordering.

Contribution

It demonstrates that including spin-orbit coupling and Coulomb repulsion in calculations accurately reproduces the experimentally observed insulating and magnetic properties of CaIrO$_3$.

Findings

Without spin-orbit coupling, CaIrO$_3$ appears metallic in calculations.

Spin-orbit coupling splits bands into $J_{eff}$ states, crucial for insulating behavior.

The material exhibits antiferromagnetic order with moments aligned along the c axis.

Abstract

I study the electronic structure and magnetism of postperovskite CaIrO$_3$ using first-principles calculations. The density functional calculations within the local density approximation without the combined effect of spin-orbit coupling and on-site Coulomb repulsion show the system to be metallic, which is in disagreement with the recent experimental evidences that show CaIrO$_3$ to be an antiferromagnetic Mott insulator in the $J_\textrm{eff}$ = 1/2 state. However, when spin-orbit coupling is taken into account, the Ir $t_{2g}$ bands split into fully filled $J_\textrm{eff}$ = 3/2 bands and half-filled $J_\textrm{eff}$ = 1/2 bands. I find that spin-orbit coupling along with a modest on-site Coulomb repulsion opens a gap leading to a Mott insulating state. The ordering is antiferromagnetic along the c axis with total moments aligned antiparallel along the c axis and canted along the b axis.