Layer-Resolved Ferromagnetic and Antiferromagnetic Proximity Effects in CrPS₄/WSe₂ Heterostructures

Magnetic proximity effects (MPE) in transition-metal dichalcogenide (TMD)-magnet heterostructures can tailor valley properties, enabling spintronic, valleytronic, and quantum functionalities. The MPE, however, is strongly influenced by the magnetic phase of the adjacent material, and active control over this phase-dependent coupling remains elusive. Here, we demonstrate layer-number-driven modulation of the MPE in air-stable CrPS₄/WSe₂ heterostructures. The valley polarization, Zeeman splitting, and in-plane optical anisotropy are dictated by the odd-even layer number of CrPS₄: even-layer CrPS₄ induces an antiferromagnetic proximity effect, yielding nearly unchanged valley polarization and an S-shaped Zeeman splitting, whereas odd-layer CrPS₄ produces a ferromagnetic proximity effect, enhancing valley polarization and generating a Z-shaped Zeeman splitting. Under an external magnetic field, the Raman polarization of WSe₂ and CrPS₄ evolves synchronously via magnon-phonon coupling. Increasing the CrPS₄ thickness suppresses interfacial charge inhomogeneity, thereby strengthening the thickness-dependent anisotropic optical response. These results uncover a direct connection between magnetic dimensionality and excitonic behavior, offering a versatile strategy for engineering valleytronic and anisotropic optical functionalities in two-dimensional quantum materials.