Layer-resolved magnetic proximity effect in van der Waals heterostructures

Magnetic proximity effects are integral to manipulating spintronic^1,2, superconducting^3,4, excitonic⁵ and topological phenomena^6-8 in heterostructures. These effects are highly sensitive to the interfacial electronic properties, such as electron wavefunction overlap and band alignment. The recent emergence of magnetic two-dimensional materials opens new possibilities for exploring proximity effects in van der Waals heterostructures^9-12. In particular, atomically thin CrI₃ exhibits layered antiferromagnetism, in which adjacent ferromagnetic monolayers are antiferromagnetically coupled⁹. Here we report a layer-resolved magnetic proximity effect in heterostructures formed by monolayer WSe₂ and bi/trilayer CrI₃. By controlling the individual layer magnetization in CrI₃ with a magnetic field, we show that the spin-dependent charge transfer between WSe₂ and CrI₃ is dominated by the interfacial CrI₃ layer, while the proximity exchange field is highly sensitive to the layered magnetic structure as a whole. In combination with reflective magnetic circular dichroism measurements, these properties allow the use of monolayer WSe₂ as a spatially sensitive magnetic sensor to map out layered antiferromagnetic domain structures at zero magnetic field as well as antiferromagnetic/ferromagnetic domains at finite magnetic fields. Our work reveals a way to control proximity effects and probe interfacial magnetic order via van der Waals engineering¹³.