Observation of disorder induced crossover in the underlying mechanism for the anomalous Hall Effect and intrinsic spin currents in Ga{sub}(1-x)Mn{sub}xAs

摘要

Since the first reports of ferromagnetic ordering in diluted magnetic semiconductors (DMS), the anomalous Hall Effect (AHE) has had a critical role in DMS research. AHE has allowed for indirect characterization of magnetic properties as well as demonstrating the novelty of carrier mediated ferromagnetic ordering in diluted magnetic semiconductors. For decades, the origins of AHE in magnetic materials have been debated extensively, and until recently, its origins had been thought as an extrinsic effect. In the initial reports of AHE in Ga{sub}(1-x)Mn{sub}xAs, by far the most studied of the DMS, the origins of AHE were assumed to be from the extrinsic skew-scattering mechanism, with a corresponding linear scaling relationship with transverse resistivity (ρ{sub}(xy)) and longitudinal resistivity (ρ{sub}(xx)). Recently, the subtlety of the quantum geometry of the Fermi surface has been recognized to describe AHE in terms of the Berry phase in momentum space. Along with investigations into the origins of ferromagnetic ordering in DMS, efforts to raise the magnetic ordering temperature (T{sub}C) has led to studies on the effects of low temperature annealing on Ga{sub}(1-x)Mn{sub}xAs, investigated by several groups with few reports of ρ{sub}(xy) quadratic dependence to ρ{sub}(xx), a scaling relationship predicted by both extrinsic side-jump mechanism origins and intrinsic origins of AHE.