Electronic structure and magnetic properties of Ca2IrO4, using first principles

Abstract

A comprehensive set of electronic structure calculations are performed to understand the origin of the insulating gap and magnetic properties of hexagonal Ca2IrO4. Although, isoelectronic with Sr2IrO4, the spin-orbit coupling driven Jeff model is anticipated to be less appropriate for Ca2IrO4 following its structural considerations. We find that the local density approximation (LDA), and those including the effects of Coulomb correlations and spin-orbit coupling fail to reproduce the experimental results. Moreover, the calculations employing the modified Becke-Johnson formalism seems to provide sufficiently good results, by predicting Ca2IrO4 to be an antiferromagnetic insulator. The origin of electronic gap is attributed to the antiferromagnetic ordering of Ir spins and the effects of spin-orbit coupling is found marginal. However, due to the anisotropy in the IrO bonding within the distorted IrO6 octahedra we deduce large magneto-anisotropic energy in Ca2IrO4. Further, our analysis shows that Ca2IrO4 is an itinerant material, suggesting that band structure effects play an important role in determining the ground state properties of iridates.