Department: Department of Physics            PI's Name: Pin-Jui Hsu

Journal: Nature Communications, 16, 7423 (2025)

Title: Atomic-Scale Visualization of Strain-Tailored Noncollinear Spin Textures in an Antiferromagnetic Ultrathin Film

Abstract: Noncollinear antiferromagnets possess intrinsic advantages moving them into the spotlight of fundamental research and opening the route toward novel spintronic applications. Crystalline strain is typically considered as an effective approach to engineer low-dimensional antiferromagnetism. Yet a direct visualization of strained-tailored noncollinear spin textures in antiferromagnetic atomic layers has not been achieved. Here, we uncover a strain-induced transition from a three-dimensional noncollinear spin state in pseudomorphic Mn bilayer to a cycloidal spin spiral with a canted rotation plane in reconstructed Mn bilayer on the Ag(111) surface. These spin states are spatially imaged on the atomic scale by spin-polarized scanning tunneling microscopy revealing the correlation of atomic and magnetic structures. As demonstrated via first-principles electronic structure theory, the three-dimensional noncollinear spin state arises from the superposition of spin spiral and antiferromagnetic order due to higher-order exchange interactions. In reconstructed Mn bilayer, by contrast, the antiferromagnetic order is hindered by interlayer exchange coupling resulting in a pure spin spiral state. Our work highlights the complex interplay of atomic structure, intra- and interlayer exchange, as well as higher-order exchange interactions at antiferromagnetically coupled interfaces.