Proximity‐Tuned Magnetic and Transport Anomalies in All‐Epitaxial Fe 5− x GeTe 2 /WSe 2 Van der Waals Heterostructures

Van der Waals (vdW) heterostructures combining two‐dimensional (2D) ferromagnets and semiconducting transition‐metal dichalcogenides (TMDCs) offer highly promising opportunities for tailoring 2D magnetism through interfacial proximity effects, enabling unique physical phenomena inaccessible in 3D systems and achieving functionalities beyond conventional spintronics. However, current fabrication of vdW heterostructures still relies heavily on the manual stacking of exfoliated 2D flakes, leading to critical challenges in scalability, interfacial quality, thickness control and device integration. This work reports on the realization of all‐epitaxial, high‐quality Fe 5− x GeTe 2 (FGT)/WSe 2 heterostructures exhibiting perpendicular magnetic anisotropy (PMA) and room‐temperature ferromagnetism. The FGT/WSe 2 system demonstrates temperature‐driven magnetic transitions, higher‐order PMA contributions and large anisotropic magnetoresistance, highlighting sublattice‐specific contributions to magnetic and transport properties. Notably, the FGT/WSe 2 heterostructures display unconventional physical phenomena, including thickness‐ and temperature‐dependent sign reversal of exchange bias, a reversed thickness trend in the unconventional Hall effect, and a non‐monotonic PMA‐thickness dependence. These anomalies indicate pronounced interfacial contributions arising from proximity effects enhanced by epitaxial interface quality. Collectively, this study provides deep insights into the magnetic and transport properties of FGT/WSe 2 vdW heterostructures, establishing a scalable platform for exploring emergent 2D physics and developing next‐generation 2D spintronic functionalities.