Persistent Large Anisotropic Magnetoresistance and Insulator-to-Metal Transition in Spin-Orbit-Coupled Sr-2(Ir1-xGax)O-4 for Antiferromagnetic Spintronics

Antiferromagnetic (AFM) spintronics, where magnetotransport is governed by an antiferromagnet instead of a ferromagnet, opens fascinating new perspectives for both fundamental research and device technology. This is because AFM spintronics have intrinsic appealing properties, such as rigidness to magnetic field, absence of stray field, and ultrafast spin dynamics. One of the urgent challenges, hindering the realization of the full potential of AFM spintronics, is the performance gap between AFM metals and insulators. Here, we demonstrate the insulator-metal transition and persistently large anisotropic magnetoresistance (AMR) in single crystals Sr-2(Ir1-xGax)O-4 (0 <= x <= 0.09), which host the same basal-plane AFM lattice with strong spin-orbit coupling. The nondoped Sr2IrO4 shows the insulating transport with AMR as large as approximately 16.8% at 50 K. The Ga substitution of Ir allows a gradual reduction of electrical resistivity. A clear insulator-to-metal transition is identified in doped samples with x above 0.05, while the AMR can still have approximately 1%, which is sizable in comparison with those in the AFM metals reported so far. Our experiments reveal that all samples have similar fourfold AMR symmetry, which can be well understood in the scenario of magnetocrystalline anisotropy. It is suggested that the spin-orbit-coupled antiferromagnets Sr-2(Ir1-xGax)O-4 are promising candidate materials for AFM spintronics, providing a rare opportunity to integrate the superior spintronic functionalities of AFM metals and insulators.