Electronic and magnetic properties of iridium ilmenites $A$IrO${}_3$ ($A=$ Mg, Zn, and Mn)

Abstract

We theoretically investigate the electronic band structures and magnetic properties of ilmenites with edge-sharing IrO${}_6$ honeycomb layers, $A$IrO${}_3$ with $A=$ Mg, Zn, and Mn, in comparison with a collinear antiferromagnet MnTiO${}_3$. The compounds with $A=$ Mg and Zn were recently reported in Y.~Haraguchi {\it et al.}, Phys. Rev. Materials {\bf 2}, 054411 (2018), while MnIrO${}_3$ has not been synthesized yet but the honeycomb stacking structure was elaborated in a superlattice with MnTiO${}_3$ in K.~Miura {\it et al.}, Commun. Mater. {\bf 1}, 55 (2020). We find that, in contrast to MnTiO${}_3$, where an energy gap opens in the Ti $3d$ bands by antiferromagnetic ordering of the high-spin $S=5/2$ moments, MgIrO${}_3$ and ZnIrO${}_3$ have a gap in the Ir $5d$ bands under the influence of both spin-orbit coupling and electron correlation. Their electronic structures are similar to those in the spin-orbit coupled Mott insulators with the $j_{\mathrm{eff}}=1/2$ pseudospin degree of freedom, as found in monoclinic $A_2$IrO${}_3$ with $A=$ Na and Li which have been studied as candidates for the Kitaev spin liquid. Indeed, we find that the effective exchange interactions between the $j_{\mathrm{eff}}=1/2$ pseudospins are dominated by the Kitaev-type bond-dependent interaction and the symmetric off-diagonal interactions. On the other hand, for MnIrO${}_3$, we show that the local lattice structure is largely deformed, and both Mn $3d$ and Ir $5d$ bands appear near the Fermi level in a complicated manner, which makes the electronic and magnetic properties qualitatively different from MgIrO${}_3$ and ZnIrO${}_3$. Our results indicate that the IrO${}_6$ honeycomb network in the ilmenites $A$IrO${}_3$ with $A=$ Mg and Zn would offer a good platform for exotic magnetism by the spin-orbital entangled moments like the Kitaev spin liquid.

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Cited by in corpus (3)

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• Asymmetric modulation of Majorana excitation spectra and nonreciprocal thermal transport in the Kitaev spin liquid under a staggered magnetic field
• Ground-State Phase Diagram of the Kitaev-Heisenberg Model on a Three-dimensional Hyperhoneycomb Lattice