A new material for probing spin-orbit coupling in Iridates

TL;DR

This paper introduces a new iridate compound with tunable electron count, demonstrating how spin-orbit coupling influences its magnetic state transition from J=1/2 to J=0.

Contribution

It reports the synthesis and magnetic characterization of a novel iridate with isolated IrO6 octahedra, highlighting the role of spin-orbit coupling in magnetic state evolution.

Findings

Magnetic susceptibility indicates a transition from J=1/2 to J=0 states.

IrO6 octahedra are highly isolated, reducing band effects.

Spin-orbit coupling dominates magnetic properties.

Abstract

We report the structure and magnetic properties of a new iridate compound, SrxLa11-xIr4O24, where the d-electron count of Ir and therefore its number of unpaired electrons can be tuned continuously from 5d5 Ir4+ to 5d4 Ir5+, i.e. from SrLa10Ir4O24 to Sr5La6Ir4O24. The IrO6 octahedra in SrxLa11-xIr4O24 are isolated from each other and from other transition elements, minimizing band effects, and the doping is on the framework sites, not the Ir sites, minimizing the effects of disorder. Measurements of the temperature dependent magnetic susceptibility are employed to determine the evolution of the Ir magnetic moment on progressing from 5d5 Ir4+ to 5d4 Ir5+, and are clearly best described by a transition from a J=1/2 to a J=0 Ir magnetic state; that is, the evolution of the magnetic susceptibility shows the dominance of spin-orbit coupling in determining the magnetic properties of a material with highly isolated IrO6 octahedra.