Spin-orbit Mott insulators with the t2g5 electron configuration are promising platforms for the Kitaev spin liquid, yet fine-tuning of their crystal structures is essential to suppress non-Kitaev interactions. Here, we investigate the local electronic structures of the ilmenite iridates AIrO3 (A=Mg,Zn,Cd) and the hyperhoneycomb β-ZnIrO3 using Ir L3-edge resonant inelastic x-ray scattering (RIXS). Multiplet analysis of the RIXS spectra reveals a systematic evolution of the crystal field and intraionic interaction parameters upon chemical substitution at the A-site. We observe an enhancement of the trigonal distortion with increasing A-site ionic radius. This provides a microscopic explanation for the deviation from the ideal J=1/2 state and the antiferromagnetic interactions identified in CdIrO3. Furthermore, the local multiplet parameters of ilmenite ZnIrO3 and hyperhoneycomb β-ZnIrO3 are found to be nearly identical, demonstrating that their different magnetic ground states are primarily governed by their distinct lattice structures rather than the single-ion properties. These findings establish a solid foundation for understanding how local crystal-field distortions control the magnetic Hamiltonian in Kitaev candidate materials.
@article{arxiv.2604.08934,
title = {Evolution of crystal field and intraionic interactions in the ilmenite $A$IrO$_3$ ($A$ = Mg, Zn, Cd) and hyperhoneycomb $\beta$-ZnIrO$_3$},
author = {Yuya Haraguchi and Hiroko Aruga Katori and Kenji Ishii and Hakuto Suzuki},
journal= {arXiv preprint arXiv:2604.08934},
year = {2026}
}