Synthesis and physical properties of the new iridium oxyfluoride Sr2Ir(O,F)6−δ using a topochemical reaction method

Abstract

We report the synthesis of a new layered iridium oxyfluoride, $\mathrm{S}{\mathrm{r}}_{2}\mathrm{Ir}{(\mathrm{O},\mathrm{F})}_{6\ensuremath{-}\ensuremath{\delta}}$, using a topochemical fluorination method. The $c$ axis is elongated compared to that in the mother compound $\mathrm{S}{\mathrm{r}}_{2}\mathrm{Ir}{\mathrm{O}}_{4}$, because the fluorine layer is inserted into the rock-salt layer while tetragonal symmetry is preserved. Resistivity measurements for the compound show nonmetallic behavior similar to that of $\mathrm{S}{\mathrm{r}}_{2}\mathrm{Ir}{\mathrm{O}}_{4}$. In magnetization measurements, suppression of antiferromagnetic order and paramagnetic behavior was observed after topochemical fluorination. Meanwhile, muon spin relaxation (\ensuremath{\mu}SR) experiments suggest the development of antiferromagnetic spin correlation between Ir spins. Furthermore, fluorine content was estimated at 1.5 the chemical composition of the fluorinated product being $\mathrm{S}{\mathrm{r}}_{2}\mathrm{Ir}{\mathrm{O}}_{x}{\mathrm{F}}_{1.5}$ with $x=3.25$, assuming $\mathrm{I}{\mathrm{r}}^{4+}$. Suppression of magnetic order in $\mathrm{S}{\mathrm{r}}_{2}\mathrm{Ir}{(\mathrm{O},\mathrm{F})}_{6\ensuremath{-}\ensuremath{\delta}}$ is attributed to antiferromagnetic instability between $\mathrm{Ir}{\mathrm{O}}_{2}$ layers by elongation of the $c$ axis due to fluorine intercalation.