Changes in magnetic properties of a 2D magnet in proximity to a 3D topological insulator*

Interactions between three-dimensional topological insulators (TIs) and magnetism can induce exotic

topological phases like the quantum anomalous Hall or axion insulator states and might be used to

harness the properties of topological insulator surface states in spintronic devices. This coupling can also

lead to changes in the magnetic properties of a ferromagnet in proximity to a topological insulator.

Here, we report measurements of changes in magnetic properties of the 2d magnet Cr₂Ge₂Te₆ in vdW

heterostructures with the 3D topological insulator BiSbTeSe₂ . We observe enhancements in both the

magnetic anisotropy and the Curie temperature compared to isolated Cr₂Ge₂Te₆ flakes. These

enhancements are tunable as the Fermi level is gated through the Dirac point of the topological

insulator. We analyze these findings In the context of interactions between the magnetic layer and

topological surface states.