Temperature and bias dependence of anisotropic magnetoresistance in antiferromagnetic Sr$_{2}$IrO$_{4}$

We study anisotropic magnetoresistance (AMR) in antiferromagnetic (AFM) Mott insulator Sr$_{2}$IrO$_{4}$ [1]. Such AMR is a promising candidate for monitoring the magnetic order parameter in AFM spintronics. Here we present temperature- and electrical bias-dependent measurements of the point-contact AMR in single crystals of Sr$_{2}$IrO$_{4}$. The point-contact technique allows to probe very small volumes and, therefore, look for electronic transport in Sr$_{2}$IrO$_{4}$ on a microscopic scale. Point-contact measurements at liquid nitrogen temperature revealed a large negative magnetoresistance (MR) for magnetic fields applied within IrO$_{2}$ a-b plane and electric currents flowing perpendicular to the plane. The observed MR decreases with increasing temperature and falls to zero at T$_{\mathrm{N\acute{e}el}}$ $\sim$ 240 K. Interestingly, the temperature dependence of MR ratios differs qualitatively from that of the resistivity. The point-contact measurements also show a strong dependence of MR on the dc bias applied to the contact. The latter can be associated with correlations between electronic transport and magnetic order in Sr$_{2}$IrO$_{4}$.\\[4pt] [1] C. Wang et al., Phys. Rev. X, November 2014.