Spin-orbit driven magnetic insulating state with ${J}_{\mathrm{eff}}\mathbf{=}1/2$ character in a 4d oxide

TL;DR

This study demonstrates that Sr4RhO6, a 4d oxide, exhibits a SOC-driven magnetic insulating state with a ${J}_{ ext{eff}}=1/2$ character, similar to 5d iridates, highlighting the role of spin-orbit coupling in 4d systems.

Contribution

The paper provides experimental and theoretical evidence that 4d oxide Sr4RhO6 has a SOC-dominated ${J}_{ ext{eff}}=1/2$ magnetic insulating ground state, expanding understanding beyond 5d iridates.

Findings

Sr4RhO6 exhibits a ${J}_{ ext{eff}}=1/2$ magnetic insulating state.

Neutron measurements show spatially separated and ideal octahedra.

Theoretical analysis confirms SOC-driven ground state.

Abstract

The unusual magnetic and electronic ground states of 5d iridates has been shown to be driven by intrinsically enhanced spin-orbit coupling (SOC). The influence of appreciable but reduced SOC in creating the manifested magnetic insulating states in 4d oxides is less clear, with one hurdle being the existence of such compounds. Here we present experimental and theoretical results on Sr$_4$RhO$_6$ that reveal SOC dominated behavior. Neutron measurements show the octahedra are both spatially separated and locally ideal, making the electronic ground state susceptible to alterations by SOC. Magnetic ordering is observed with a similar structure to an analogous ${J}_{\mathrm{eff}}\mathbf{=}1/2$ Mott iridate. We consider the underlying role of SOC in this rhodate with density functional theory and x-ray absorption spectroscopy and find a magnetic insulating ground state with ${J}_{\mathrm{eff}}\mathbf{=}1/2$ character.