Anisotropic magnetoresistance reversal in a two-dimensional helical antiferromagnet

The helimagnetic order describes a non-collinear spin texture of antiferromagnets, arising from competing exchange interactions. Although collinear antiferromagnets are elemental building blocks of antiferromagnetic (AFM) spintronics, the potential of implementing spintronic functionality in non-collinear antiferromagnets has not been clarified thus far. In this study, we propose an AFM helimagnet of EuCo₂As₂ as a novel single-phase spintronic material that exhibits an unconventional reversal behavior of the anisotropic magnetoresistance (AMR) effect. The contrast in the AMR arises from two electrically distinctive magnetic phases with spin-flop-driven switching from positive to negative magnetoresistance along the easy axis. Remarkably, an easy-plane anisotropic spin model reproduces the aspects of magnetic and magnetotransport properties, indicating that the highly two-dimensional magnetocrystalline anisotropy is essential in the observed spintronic functionality. The switchable antiferromagnetic memory states formed by integrating intrinsic bulk properties simplifies the stacking geometry and thus provides a more expandable platform to construct sophisticated heterostructures.