Interpretation of experimental evidence of the topological Hall effect

The topological Hall effect in magnetic materials is considered the ultimate trademark of the skyrmion phase. The phenomenon is identified by distinct non-monotonic features in the Hall effect signal presumed to be the evidence of the topological origin. It is demonstrated here that similar features, unrelated to the skyrmion physics, arise in heterogeneous ferromagnets when components of the material exhibit the extraordinary Hall effect with opposite polarities. Relevance of this mechanism to the published data is discussed.