Exchange Bias in Molecule/Fe₃GeTe₂ van der Waals Heterostructures via Spinterface Effects

The exfoliation of layered magnetic materials generates atomically thin flakes characterized by an ultrahigh surface sensitivity, which makes their magnetic properties tunable via external stimuli, such as electrostatic gating and proximity effects. Another powerful approach to engineer magnetic materials is molecular functionalization, generating hybrid interfaces with tailored magnetic interactions, called spinterfaces. However, spinterface effects have not yet been explored on layered magnetic materials. Here, the emergence of spinterface effects is demonstrated at the interface between flakes of the prototypical layered magnetic metal Fe₃GeTe₂ and thin films of Co-phthalocyanine. Magnetotransport measurements show that the molecular layer induces a magnetic exchange bias in Fe₃GeTe₂, indicating that the unpaired spins in Co-phthalocyanine develop antiferromagnetic ordering and pin the magnetization reversal of Fe₃GeTe₂ via magnetic proximity. The effect is strongest for a Fe₃GeTe₂ thickness of 20 nm, for which the exchange bias field reaches −840 Oe at 10 K and is measurable up to ≈110 K. This value compares very favorably with previous exchange bias fields reported for Fe₃GeTe₂ in all-inorganic van der Waals heterostructures, demonstrating the potential of molecular functionalization to tailor the magnetism of van der Waals layered materials.