Structural, electronic, and magnetic properties of nearly-ideal $J_{\mathrm{eff}}$ $=$ 1/2 iridium halides

Abstract

Heavy transition metal magnets with $J_{\mathrm{eff}}$ $=$ 1/2 electronic ground states have attracted recent interest due to their penchant for hosting new classes of quantum spin liquids and superconductors. Unfortunately, model systems with ideal $J_{\mathrm{eff}}$ $=$ 1/2 states are scarce due to the importance of non-cubic local distortions in most candidate materials. In this work, we identify a family of iridium halide systems [i.e. K${}_2$IrCl${}_6$, K${}_2$IrBr${}_6$, (NH${}_4$)${}_2$IrCl${}_6$, and Na${}_2$IrCl${}_6\cdot$ 6(H${}_2$O)] with Ir${}^{4+}$ electronic ground states in extremely close proximity to the ideal $J_{\mathrm{eff}}$ $=$ 1/2 limit, despite a variation in the low-temperature global crystal structures. We also find ordered magnetic ground states for the three anhydrous systems, with single crystal neutron diffraction on K${}_2$IrBr${}_6$ revealing Type-I antiferromagnetism. This spin configuration is consistent with expectations for significant Kitaev exchange in a face-centered-cubic magnet.

14 pages, 9 figures