Polarized neutron reflectivity of all-van der Waals Dirac semimetal/2D ferromagnet heterostructures

The topological hall effect (THE) has been proposed as an indicator of topologically nontrivial magnetic structures such as skyrmions, which have incredible technological potential. However, the THE may also be generated by nonuniform magnetism, such as a difference in preferred spin direction at the surface and bulk of a material. These effects are particularly pronounced in ultrathin films where the surface and bulk regions have comparable contributions to the electrical properties. The 2D van der Waals materials CrTe2 is reported to show these interesting properties, and we observe a large THE. In order to determine whether the THE originates in nonuniform magnetism or topologically nontrivial chiral magnetic structures, we propose to use polarized neutron reflectometry to probe the uniformity of the magnetic depth profile in CrTe2 thin films.