Persistent large anisotropic magnetoresistance and insulator to metal transition in spin-orbit coupled antiferromagnets Sr2(Ir1-xGax)O4

Abstract: Antiferromagnetic (AFM) spintronics, where magneto-transport is governed by an antiferromagnet instead of a ferromagnet, opens fascinating new perspectives for both fundamental research and device technology, owing to their intrinsic appealing properties like 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, has been the performance gap between AFM metals and insulators. Here, we demonstrate the insulator-metal transition and persistently large anisotropic magnetoresistance (AMR) in single crystals Sr2(Ir1-xGax)O4 (0<x<0.09) which host the same basal-plane AFM lattice with strong spin-orbit coupling. The non-doped Sr2IrO4 shows the insulating transport with the AMR as big as ~16.8% at 50 K. The Ga substitution of Ir allows a gradual reduction of electrical resistivity, and a clear insulator-to-metal transition is identified in doped samples with x above 0.05, while the AMR can still have ~1%, sizable in comparison with those in AFM metals reported so far. Our experiments reveal that all the samples have the similar fourfold AMR symmetry, which can be well understood in the scenario of magnetocrystalline anisotropy. It is suggested that the spin-orbit coupled antiferromagnets Sr2(Ir1-xGax)O4 are promising candidate materials for AFM spintronics, providing a rare opportunity to integrate the superior spintronic functionalities of AFM metals and insulators.