  Magnetic proximity effects are crucial ingredients for engineering
spintronic, superconducting, and topological phenomena in heterostructures.
Such effects are highly sensitive to the interfacial electronic properties,
such as electron wave function overlap and band alignment. The recent emergence
of van der Waals (vdW) magnets enables the possibility of tuning proximity
effects via designing heterostructures with atomically clean interfaces. In
particular, atomically thin CrI3 exhibits layered antiferromagnetism, where
adjacent ferromagnetic monolayers are antiferromagnetically coupled. Exploiting
this magnetic structure, we uncovered 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 found 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. These properties
enabled us to use 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 near the spin-flip transition
in bilayer CrI3. Our work reveals a new way to control proximity effects and
probe interfacial magnetic order via vdW engineering.
