Hall effect and the magnetotransport properties of Co2MnSi1-xAlx Heusler alloys

We have investigated the transport properties of the quaternary Heusler alloys Co2MnSi1-xAlx (0≤x≤1), which have been theoretically predicted to develop a half-metallic band structure as x→0. Resistivity versus temperature measurements as a function of Al concentration (x) revealed a systematic reduction in the residual resistivity ratio as well as a transition from weakly localized to half-metallic conduction as x→0. From measurements of the ordinary and anomalous Hall effects, the charge carrier concentration was found to increase, while the anomalous Hall coefficient decreased by nearly an order of magnitude with each sample as x→0 (Δx=0.25.). Scaling of the anomalous Hall effect with longitudinal resistivity reveals that both the skew-scattering and intrinsic contributions grow quickly as x→1, indicating that disorder and band-structure effects cause the large anomalous Hall effect magnitudes observed for Co2MnAl.