Spin-transfer and topological Hall effects in itinerant frustrated magnets

Magnetically frustrated platforms have resurged in spintronics as optimal candidates for hosting three dimensional topological spin textures (e.g., Shankar skyrmions and 4 pi-vortices) as well as topological defects (e.g., magnetic disclinations). These topological excitations are encoded in the noncollinear order emerging at the mesoscale from the measurement of the spin-spin correlation, and have not been observed experimentally so far due to the absence of probes coupling directly to this exotic rotation-matrix order parameter. In this work we examine the spin-transfer and topological Hall physics of metallic frustrated magnets and show that SO(3) solitons and magnetic disclinations mediate previously unidentified contributions to the corresponding effects, with no analog in collinear magnetism. In particular, we present a minimal low-energy long-wavelength theory of the Yang-Mills type for the itinerant carriers and also discuss the emergent electrodynamics mediated by the topological solitons/defects arising in the noncoplanar magnetic background. We also considered the effect of symmetry reduction (with respect to the case of full rotational symmetry) on both spin-transfer and topological Hall responses of the magnetic conductor. Furthermore, we discuss experimental setups for the detection of the aforesaid Hall currents. Our findings open new avenues for the detection of topological solitons/defects in magnetic systems with order-parameter manifolds beyond the conventional S2 paradigm.

Automated summary

Magnetically frustrated platforms are considered as optimal candidates for hosting topological spin textures and defects. However, these have not been observed experimentally due to the lack of probes coupling directly to the exotic rotation-matrix order parameter. In this work, the spin-transfer and topological Hall physics of metallic frustrated magnets are examined, and new contributions mediated by SO(3) solitons and magnetic disclinations are identified. The effect of symmetry reduction on the spin-transfer and topological Hall responses is also discussed, as well as experimental setups for detecting Hall currents.