Topological Hall Effect in Itinerant Helimagnets

Abstract

AbstractIn this chapter, we focus on the topological Hall effect in itinerant helimagnets. As described in Chap. 1, there have been few helimagnets which show topological Hall effect except for Skyrmion lattice phases of chiral helimagnets (e.g. MnSi and MnGe). This is because the total scalar spin chirality summed over the whole lattice sites often becomes zero due to structural symmetry, although the noncoplanar spin configuration is generally realized in helical magnets under applied \(H\). In the first and second sections of this chapter, we report two new examples of helimagnets in which the scalar spin chirality does not cancel out owing to the modulation of spin structure by DM interaction and thus topological Hall effect occurs. In the third section, we investigate the topological Hall effects by heat current, i.e. topological thermal Hall effect and topological Nernst effect, for MnGe. In contrast to the cases of MnSi and (Fe,Co)Si, the Skyrmion lattice phase of MnGe has been considered to prevail in wide temperature and magnetic-field window. This enables us to examine thoroughly the topological Hall effects by heat current in the Skyrmion lattice phase.KeywordsTopological Hall effectItinerant helimagnetScalar spin chiralityDzyaloshinsky-Moriya interactionBerry phase of electrons