Emergence of topological Hall effect from fanlike spin structure as modified by Dzyaloshinsky-Moriya interaction in MnP

A nontrivial Hall effect has been observed as an anomaly of the Hall conductivity in the magnetization process in a typical itinerant helimagnet MnP. Since the Dzyaloshinsky-Moriya interaction slightly modulates the spin structure, the anomaly is identified only in the specific magnetic (fanlike) phase that can have finite scalar spin chirality. The decrease in the magnitude of the anomaly as observed by doping Co is well accounted for in terms of the topological Hall effect arising from the spin-chirality-induced Berry phase in real space. A fictitious magnetic flux in real space is estimated to be similar to 1 T, which is consistent with the small modulation of the spin structure.