Disordered magnetism in the double perovskite LaCaScIrO6 with a distorted fcc lattice of Ir4+

Abstract

The synthesis and characterization of the previously unknown material LaCaScIrO${}_6$ is reported. LaCaScIrO${}_6$ presents a new example of the rare case of a double perovskite with the strongly spin-orbit coupled 5\textit{d}-ion Ir${}^{4+}$ as its only magnetic species, forming a monoclinically distorted version of the frustrated fcc lattice. Magnetization measurements show a weak anomaly at 8~K. The Curie-Weiss temperature Θ${}_{CW}$ and effective magnetic moment μ${}_{eff}$ of LaCaScIrO${}_6$ are in close proximity to the related compound La${}_2$MgIrO${}_6$ but differ from La${}_2$ZnIrO${}_6$. This suggests that the nature of the non-magnetic \textit{B}-ion, namely its \textit{d}-orbital filling has a strong influence on the magnetic properties. The \textit{d}${}^0$-ions Sc${}^{3+}$ and Mg${}^{2+}$ allow a different kind of exchange interactions within the Ir-sublattice than the \textit{d}${}^{10}$-ion Zn${}^{2+}$. In addition, ac-susceptibility data does not show signs of a spin-glass ground state. The nature of the magnetism in LaCaScIrO${}_6$ has been further elucidated using muon spin relaxation measurements. The zero-field measurements reveal the absence of well defined oscillations down to 1.6\,K, while temperature dependent $\mu$SR studies show an anomaly at 8\,K. Overall, our results suggest the presence of two different magnetic environments or domains in LaCaScIrO${}_6$, which is likely related to its structural features.

References in corpus (1)

• Revisiting the Kitaev material candidacy of Ir4+ double perovskite iridates