Phase inhomogeneity and inapplicability of Jeff=0 description in dilute Ir5+ doped Ba2YSb1-xIrx O6 (x=0.1, 0.2, 0.3) PHASE INHOMOGENEITY and INAPPLICABILITY of ... KHAN, MENEGHINI, BERT, SALA, and RAY

Various exotic magnetic ground states have been anticipated in the higher transition metal (4d and 5d) oxides with large atomic spin-orbit coupling (SOC). However, many such expectations were not met because the exact atomic SOC strength and its consequent influence on electronic and magnetic ground states were always masked by solid-state effects. Here, we attempt to dope a dilute amount of Ir5+ (x=0.1-0.3) in place of Sb5+ in perfectly cubic Ba2YSbO6 with a target to minimize the effects of hopping between distant Ir ions and noncubic crystal field effect to promote the effect of SOC and to realize the coveted Jeff=0 ground state, expected for jj-coupled 5d4Ir5+ systems, purely from the consideration of atomic SOC. However, despite certain inhomogeneity in the distribution of the dopant Ir5+ ions in the system, our experimental results reveal high magnetic moments (away from the Jeff = 0 picture) with strong nearest-neighbor interaction, but without any long-range ordering, for the lowest doped system which continues to decrease with increasing Ir content, completely contrary to the expectation of the jj-coupling description. This observation strongly indicates that presence of a localized Ir moment, originating from L-S coupling interaction, might be the most appropriate mechanism here.