Enhanced contribution of surface state and modification of magnetoresistance in FexBi2−xSe3 topological insulator crystals

Abstract

Magnetic atomic-doped topological insulator crystals with the formula FexBi2−xSe3 were fabricated using the self-flux method and their electrical and magnetic transport properties were studied. All samples showed weakly metallic resistivity and the resistivity increased monotonously as the Fe concentration increased. Conductivity was modified by Fe at high- and low-temperature regions via different mechanisms, which could be explained by the freezing of bulk carriers around 30 K. For highly doped samples, simultaneous crossovers in the curves of temperature dependent of resistivity (ρ-T) and temperature dependent of magnetoresistance (MR-T) at low temperature were observed, indicating that the contribution of the surface state was significantly improved. No obvious enhanced surface effect was observed in samples doped with low concentration of Fe, but the MR was enhanced significantly in low-doped samples and suppressed by high Fe content. Magnetic-field-induced metal-insulator transitions were observed in the samples with the largest MR values. The change in MR was related to three mechanisms: phonon scattering effect, magnetic ordering, and spin disorder scattering.