Scattering mechanisms in textured FeGe thin films: Magnetoresistance and the anomalous Hall effect

摘要

A textured thin film of FeGe was grown by magnetron sputtering with a helimagnetic ordering temperature of T_N = 276 ± 2 K. From 5 K to room temperature, a variety of scattering processes contribute toward the overall longitudinal and Hall resistivities. These were studied by combining magnetometry and magnetotransport measurements. The high-field magnetoresistance (MR) displays three clear temperature regimes: Lorentz force MR dominates at low temperatures, above T ≈ 80 K scattering from spin-waves predominates, while finally for T approx＞ 200 K scattering from fluctuating local moments describes the MR. At low fields, where the magnetization is no longer technically saturated, we find a scaling of magnetoresistance with the square of the magnetization, indicating that the MR due to the unwinding of spins in the conical phase arises from a similar mechanism to that in magnetic domain walls. This MR is only visible up to a temperature of about 200 K. No features can be found in the temperature or field dependence of the longitudinal resistivity that belie the presence of the underlying magnetic phase transition at T_N: the marked changes in behavior are at much lower temperatures. The anomalous Hall effect has a dramatic temperature dependence in which the anomalous Hall resistivity scales quadratically with the longitudinal resistivity: comparison with anomalous Hall scaling theory shows that our system is in the intrinsic "moderately dirty" regime. Lastly, we find evidence of a topological Hall effect of size ～100 μΩ cm.