Magnetic ground state of the dimer-based hexagonal perovskite Ba$_{3}$ZnRu$_{2}$O$_{9}$

TL;DR

This study uses RIXS and magnetic susceptibility to determine that Ba$_{3}$ZnRu$_{2}$O$_{9}$ has an $S=3/2$ dimer ground state, clarifying its magnetic nature and demonstrating spectroscopic fingerprinting's effectiveness.

Contribution

The paper provides direct spectroscopic evidence confirming the $S=3/2$ ground state in Ba$_{3}$ZnRu$_{2}$O$_{9}$, resolving previous ambiguities from powder studies.

Findings

RIXS spectra reveal Hund's multiplet and intradimer spin-triplet excitations.

The observed transition energies match the $S=3/2$ ground state.

High-temperature susceptibility supports the $S=3/2$ dimer model.

Abstract

We investigate the magnetic ground state of single crystals of the ruthenium-dimer-based hexagonal perovskite Ba$_{3}$ZnRu$_{2}$O$_{9}$ using magnetic susceptibility and resonant inelastic x-ray scattering (RIXS) measurements. While a previous study on powder samples exhibited intriguing magnetic behavior, questions about whether the spin state within a Ru$_{2}$O$_{9}$ dimer is a conventional $S = 3/2$ dimer or an orbital-selective $S = 1$ dimer were raised. The RIXS spectra reveal magnetic excitations from Hund's intraionic multiplet and intradimer spin-triplet transitions. The observed transition energies of the Hund's intraionic multiplets align with the $S=3/2$ ground state, contrasting with the theoretically proposed orbital-selective $S=1$ dimer state. High-temperature magnetic susceptibility analysis confirms the realization of the spin $S=3/2$ dimer state, and the extracted intradimer coupling is consistent with the spin-triplet transition energy observed in the RIXS spectra. These results highlights the ability of "spectroscopic fingerprinting" by RIXS to determine the magnetic ground states of complex materials.