Anisotropic magnetoresistance in Sr$_{2}$IrO$_{4}$

We report the first measurements of the point-contact magnetoresistance (MR) of antiferromagnetic semiconductor Sr$_{2}$IrO$_{4}$. The point-contact technique allows to probe very small volumes associated with point contacts and, therefore, looks for electronic transport on a microscopic scale. Point-contact measurements with single crystals of Sr$_{2}$IrO$_{4}$ were intended to see if the additional local resistance associated with a small contact area between a sharpened Cu tip and the antiferromagnet shows MR such as that seen in bulk crystals. The Sr$_{2}$IrO$_{4}$ crystals were grown by the flux method. Point-contact measurements at liquid nitrogen temperature revealed large MRs (up to 8{\%}) for modest magnetic fields (250 mT) applied within IrO$_{2}$ (ab) plane. The angular dependence of MR shows a crossover from four-fold to two-fold symmetry with an increasing magnetic field which may be tentatively attributed to the field-induced changes of antiferromagnetic order within IrO$_{2}$ planes. The observed MR can be potentially used to sense the antiferromagnetic order in spintronic applications.