Giant Spin-flop magnetoresistance in a collinear antiferromagnetic tunnel junction

Collinear antiferromagnetic (AFM) materials have the unique promise of no stray fields, displaying ultrafast dynamics, and being robust against perturbation fields which motivate the extensive research of antiferromagnetic spintronics. However, the detection of antiferromagnetic order poses formidable challenges. Here, we report the electrical detection of colinear antiferromagnetism in all-epitaxial RuO₂/MgO/RuO₂ tunnel junctions (TJ) using spin-flop tunneling anisotropic magnetoresistance (TAMR). We measured a TAMR ratio of around 60% at room temperature, which arises from the switching between the parallel and perpendicular configurations of the adjacent collinear AFM state. Furthermore, we carried out angular-dependent measurements using this antiferromagnetic tunnel junction (AFM-TJ) and showed that the magnitude of anisotropic longitudinal magnetoresistance in the AFM-TJ can be controlled by the direction of an external magnetic field. First principles electronic structure calculations corroborate that the collinear antiferromagnetic TJ may produce a substantially large TAMR ratio. The emergence of resonant interfacial states, combined with the tunneling transmission through the MgO barrier and the substantial spin-orbit coupling (SOC) strength of Ru, especially when augmented by oxygen doping, leads to the significant enhancement observed in the tunneling anisotropic magnetoresistance (TAMR). Our work not only propels antiferromagnetic materials to the forefront of spintronic device innovation but also unveils a novel paradigm for electrically controlled antiferromagnetic spintronics, auguring transformative advancements in high-speed, low-energy information devices.