Antiferromagnet-Based Spintronic Functionality by Controlling Isospin Domains in a Layered Perovskite Iridate

The novel electronic state of the canted antiferromagnetic (AFM) insulator strontium iridate (Sr₂IrO₄) is well described by the spin–orbit-entangled isospin J_eff = 1/2, but the role of isospin in transport phenomena remains poorly understood. In this study, antiferromagnet-based spintronic functionality is demonstrated by combining the unique characteristics of the isospin state in Sr₂IrO₄. Based on magnetic and transport measurements, a large and highly anisotropic magnetoresistance (AMR) is obtained by manipulating the AFM isospin domains. First-principles calculations suggest that electrons whose isospin directions are strongly coupled to the in-plane net magnetic moment encounter an isospin mismatch when moving across the AFM domain boundaries, which generates a high resistance state. By rotating a magnetic field that aligns in-plane net moments and removes domain boundaries, the macroscopically ordered isospins govern dynamic transport through the system, which leads to the extremely angle-sensitive AMR. As this work establishes a link between isospins and magnetotransport in strongly spin–orbit-coupled AFM Sr₂IrO₄, the peculiar AMR effect provides a beneficial foundation for fundamental and applied research on AFM spintronics.