Out-of-plane surface magnetization in Fe₅GeTe₂ induced by magnetic coupling with NiPS3

In this talk, we present our recent comprehensive investigation on Fe₅GeTe₂/NiPS₃ heterostructure with element-specific measurements. Fe₅GeTe₂ is a van der Waals ferromagnet which was reported to possess a thickness- and temperature- dependent spin-reorientation transition. NiPS₃ is an in-plane van der Waals antiferromagnet with a weak uniaxial anisotropy along the a-axis of its monoclinic lattice. Micron-sized Fe₅GeTe₂/NiPS₃ heterostructures were transferred onto membrane window TEM grids for the characterizations with non-microscopic X-ray techniques. Through element-specific X-ray magnetic circular dichroism (XMCD), X-ray magnetic linear dichroism (XMLD), photoemission electron microscopy (PEEM) and local probe electronic transport measurements, we directly observed the XMLD and tri-axial in-plane antiferromagnetic domains in NiPS₃, and investigated the interfacial coupling effects on the ferromagnetic properties of Fe₅GeTe₂. We observed an interfacial-coupling induced magnetic anisotropy (PMA) in Fe₅GeTe₂. This extrinsic interfacial magnetic anisotropy influences the Fe₅GeTe₂ magnetizations within a small thickness near the interface, resulting in a spin texture along the perpendicular direction of the film. The discovery of spin texture along the perpendicular direction is a unique property of van der Waals magnetic thin films due to their weak interlayer coupling. Our work shows another novel and unique characteristics of van der Waals magnetic materials.