Magnetic phase diagram of Sr2−xLaxIrO4 synthesized by mechanical alloying

We report the crystal structure and physical properties of $\mathrm{S}{\mathrm{r}}_{2\ensuremath{-}x}\mathrm{L}{\mathrm{a}}_x\mathrm{Ir}{\mathrm{O}}₄$ synthesized by mechanical alloying. The magnetic transition temperature ${T}_{\mathrm{N}}$ and electrical resistivity decreased with increasing La doping, consistent with previous studies involving single-crystalline samples. We also identified the relationship between ${T}_{\mathrm{N}}$ and tetragonal distortion ($c/a$) in this system. This result suggests that the magnetism of the Sr214 system is strongly correlated with its crystal structure. Zero-field muon spin rotation/relaxation studies revealed that short-range antiferromagnetic ordering is realized in $\mathrm{S}{\mathrm{r}}_1.9\mathrm{L}{\mathrm{a}}_0.1\mathrm{Ir}{\mathrm{O}}₄$; also, the spin-glass state is stabilized in the low-temperature region. The Ir moment estimated from the longitudinal field \ensuremath{\mu}SR results is $0.045\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$, ten times smaller than that of $\mathrm{S}{\mathrm{r}}₂\mathrm{Ir}{\mathrm{O}}₄$ ($\ensuremath{\sim}0.4\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{\mathrm{B}}$), indicating that electrons are introduced into the Ir atoms.