Sr4 –xCaxRhO6: a magnetically ordered RhIV compound

Abstract

Sr_{4 –x}Ca_xRhO₆(x= 0,1) has been prepared at ambient pressure using the standard techniques of solid-state chemistry. Profile analysis of the X-ray powder diffraction (XRPD) data shows that the rhombohedral product is isostructural with Sr₄IrO₆. It thus contains Rh^IV cations in octahedral sites and alkaline-earth-metal cations in trigonal prismatic coordination. The mean Rh—O distance is 2.04 Å. Both of the compositions studied order antiferromagnetically at ca. 7 K. The magnetic susceptibility data have been analysed using both a Curie-Weiss Law (µ_eff^{300 K}= 2.03 µ_B for x= 0) and the one dimensional (1D) Ising model [J/k=- 3.30(1) K for x= 0].