Magnetic properties of Mn-doped Sr2IrO4

In 5d electron transition metal oxides, interplay between spin-orbit coupling and electronic interactions can lead to novel properties. One example is the Mott state in Sr$_2$IrO$_4$ which is believed to be associated with the formation of a J$_{eff}$=1/2 band due to large spin-orbit splitting of the t$_{2g}$ band. We use bulk measurements and resonant magnetic x-ray scattering to explore the effects of substituting Mn for Ir in single crystals of Sr$_2$Ir$_{0.9}$Mn$_{0.1}$O$_4$. These measurements indicate that 10\% Mn doping is sufficient to suppress the magnetic ordering temperature from 240 K to ~155 K. Resonant magnetic x-ray scattering measurements indicate a change in the long-range magnetic order when compared to that of undoped Sr$_2$IrO$_4$. Despite the large change in transition temperature and the altered magnetic structure, we observe a difference in the resonant enhancement between the L$_2$ and L$_3$ edges which is very similar to that seen in the pure material. This suggests that the magnetic structure of Sr$_2$IrO$_4$ can be altered by small perturbations whereas the J$_{eff}$=1/2 state is robust.