Phase inhomogeneity and inapplicability of Jeff=0 description in dilute Ir5+ doped Ba2YSb1−xIrxO6 (x=0.1, 0.2, 0.3)

Abstract

Various exotic magnetic ground states have been anticipated in the higher transition metal $(4d \mathrm{and} 5d)$ 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 ${\mathrm{Ir}}^{5+}$ $(x=0.1--0.3)$ in place of ${\mathrm{Sb}}^{5+}$ in perfectly cubic ${\mathrm{Ba}}_{2}{\mathrm{YSbO}}_{6}$ 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 ${J}_{\text{eff}}=0$ ground state, expected for $jj$-coupled $5{d}^{4}\phantom{\rule{4pt}{0ex}}{\mathrm{Ir}}^{5+}$ systems, purely from the consideration of atomic SOC. However, despite certain inhomogeneity in the distribution of the dopant ${\mathrm{Ir}}^{5+}$ ions in the system, our experimental results reveal high magnetic moments (away from the ${J}_{\text{eff}}$ = 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 $L\text{\ensuremath{-}}S$ coupling interaction, might be the most appropriate mechanism here.