Classical mechanism for the anomalous enhancement of Hall resistivity during magnetization reversal

Certain bulk or synthetic ferromagnetic conductors with broken inversion symmetry show a characteristic hump in the hysteresis curve of the Hall resistivity, which is commonly ascribed to the topological Hall effect due to the formation of skyrmion lattice in finite fields. Here we argue that the hump could also be due to classical mechanisms associated with transport in random media. By modeling a 2D inhomogeneous ferromagnetic conductor using a random resistor network model, we are able to show that an anomalous enhancement of the Hall resistivity can arise before the ferromagnet is fully switched by a perpendicular magnetic field. The qualitative behavior is further analyzed by solving the diffusion equation with correlated disorder perturbatively.