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Electronic structure of the frustrated diamond lattice magnet NiRh$_2$O$_4$

Authors :
Zager, B.
Chamorro, J. R.
Ge, L.
Bisogni, V.
Pelliciari, J.
Li, J.
Fabbris, G.
McQueen, T. M.
Mourigal, M.
Plumb, K. W.
Publication Year :
2022
Publisher :
arXiv, 2022.

Abstract

The $A$-site spinel NiRh$_2$O$_4$ is the only known realization of a spin-1 diamond lattice magnet and is predicted to host unconventional magnetic phenomena driven by frustrated nearest and next-nearest neighbor exchange as well as orbital degeneracy. Previous works found no sign of magnetic order but found a gapped dispersive magnetic excitation indicating a possible valence bond magnetic ground state. However, the presence of many competing low energy degrees of freedom and limited empirical microscopic constraints complicates further analysis. Here, we carry out resonant inelastic x-ray scattering (RIXS) and x-ray absorption spectroscopy (XAS) to characterize the local electronic structure of NiRh$_2$O$_4$. The RIXS data can be partly described by a single-ion model for tetrahedrally coordinated Ni$^{2+}$ and indicates a tetragonal distortion $\Delta t_2\!=\!70$ meV that splits the $t_2$ orbitals into a high energy orbital singlet and lower energy orbital doublet. We identify features of the RIXS spectra that are consistent with a Rh-Ni two-site excitation indicating strong metal-metal hybridization mediated by oxygen in NiRh$_2$O$_4$. We also identify signatures of electron-phonon coupling through the appearance of phonon sidebands that dress crystal field excitations. These results establish the key energy scales relevant to the magnetism in NiRh$_2$O$_4$ and further demonstrate that covalency and lattice dynamics play essential roles in controlling the magnetic ground states of $A$-site spinels.

Details

Database :
OpenAIRE
Accession number :
edsair.doi.dedup.....f3d17d87c95c171cb3c9adcedb4dbfb6
Full Text :
https://doi.org/10.48550/arxiv.2205.12296