New material for probing spin-orbit coupling in iridates

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 5d5Ir4+ to 5d4Ir5+, 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 5d5Ir4+ to 5d4Ir5+, and are clearly best described by a transition from a J=1/2 to a J=0Ir 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. © 2015 American Physical Society.