Anomalous Hall effect and magnetoresistance in the layered ferromagnet Fe14 Ta S2: The inelastic regime

The large magnetic anisotropy in the layered ferromagnet Fe14 Ta S2 leads to very sharp reversals of the magnetization M at the coercive field. We have exploited this feature to measure the anomalous Hall effect (AHE), focusing on the AHE conductivity σ xy A in the inelastic regime. At low temperature T (5-50 K), σ xy A is T independent, consistent with the Berry-phase/Karplus-Luttinger theory. Above 50 K, we extract an inelastic AHE conductivity σ xy in that scales as the square of Δρ (the T dependent part of the resistivity ρ). The term σ xy in clarifies the T dependence and sign reversal of the AHE coefficient Rs (T). We discuss the possible ubiquity of σ xy in in ferromagnets and ideas for interpreting its scaling with (Δρ)2. Measurements of the magnetoresistance (MR) reveal a rich pattern of behavior vs T and field-tilt angle. We show that the two mechanisms, the anisotropic MR effect and field suppression of magnons, account for the intricate MR behavior, including the bow-tie features caused by the sharp reversals in M.