Electronic and Magnetic Characterization of Epitaxial CrBr Monolayers on a Superconducting Substrate.

The ability to imprint a given material property to another through a proximity effect in layered 2D materials has opened the way to the creation of designer materials. Here, molecular-beam epitaxy is used for direct synthesis of a superconductor-ferromagnet heterostructure by combining superconducting niobium diselenide (NbSe ) with the monolayer ferromagnetic chromium tribromide (CrBr ). Using different characterization techniques and density-functional theory calculations, it is confirmed that the CrBr monolayer retains its ferromagnetic ordering with a magnetocrystalline anisotropy favoring an out-of-plane spin orientation. Low-temperature scanning tunneling microscopy measurements show a slight reduction of the superconducting gap of NbSe and the formation of a vortex lattice on the CrBr layer in experiments under an external magnetic field. The results contribute to the broader framework of exploiting proximity effects to realize novel phenomena in 2D heterostructures.