Electrical and magnetic transport properties of Co-doped Bi2Se3 topological insulator crystals

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Abstract
Transition metal doped topological insulators (TI) Co x Bi 2-x Se 3 were prepared and the phase structure, electrical and magnetic transport properties, Hall mobility and Hall resistivity were studied. The lattice constant c decreased with the increasing Co concentration. All samples exhibited weak metallic resistivity. With increasing Co concentration, the value of ρxx increased, reaching a maximum at x = 0.02, and then decreased. The resistivity data could be fitted by different formulas below and above 30 K in all samples result from different mechanism corresponding to different temperature regions. The magnetoresistance (MR) of Bi 2 Se 3 TI showed a change dependence of concentration. The MR was enhanced by small quantity of Co doping, attaining a maximum value in Bi 1.98 Co 0.02 Se 3 crystal; but MR was suppressed in high-doped sample (x > 0.02). Those results were ascribed to the rivalry between the phonon scattering effect and the magnetic ordering in single crystals caused by Co ions. For low-doped samples doped, the contribution of phonon scattering was much higher than that of magnetic ordering, leading to larger MR value. However, in samples doped with higher Co concentrations, the magnetic ordering effect became dominant and caused the MR decreases. The MR increased with decreasing temperature and increasing magnetic field. The Hall mobility data indicated that incorporating Co in Bi 2 Se 3 single crystal can reduce native defect of Bi 2 Se 3.

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