Spin Frustration and Unconventional Surface Spin Canting State in Van der Waals Ferromagnet/Antiferromagnet Heterostructures.

Wang, Tianye; Li, Qian; Yang, Mengmeng; Sun, Yu; N'Diaye, Alpha T; Klewe, Christoph; Scholl, Andreas; Chen, Xianzhe et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

Atomically flat surfaces of van der Waals (vdW) materials pave an avenue for addressing a long-standing fundamental issue of how a compensated antiferromagnet (AFM) surface frustrates a ferromagnetic (FM) overlayer in FM/AFM heterostructures. We investigate Fe<sub>5</sub>GeTe<sub>2</sub>/NiPS<sub>3</sub> vdW heterostructures by characterizing AFM and FM spins separately. We find that in-plane zig-zag AFM NiPS<sub>3</sub> develops three equivalent AFM domains, which are robust against external magnetic field and magnetic coupling with Fe<sub>5</sub>GeTe<sub>2</sub>. Moreover, evidence is provided of in-plane-AFM-induced perpendicular magnetic anisotropy (PMA) in adjacent Fe<sub>5</sub>GeTe<sub>2</sub>, and an unconventional out-of-plane surface spin canting state with the Fe<sub>5</sub>GeTe<sub>2</sub> spins spatially turn from out-of-plane direction near the interface to in-plane direction away from the interface in Fe<sub>5</sub>GeTe<sub>2</sub>/NiPS<sub>3</sub>. The out-of-plane surface spin canting is a unique property of spin frustration in vdW magnetic heterostructures.