Two-carrier transport in SrMnBi2 thin films
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Monocrystalline SrMnBi2 thin films were grown by molecular beam epitaxy (MBE), and their transport properties were investigated. A high and unsaturated linear magnetoresistance (MR) was observed, which exhibited a transition from a semi-classical weak-field B 2 dependence to a high-field linear dependence. An unusual nonlinear Hall resistance was also observed because of the anisotropic Dirac fermions. The two-carrier model was adopted to analyze the unusual Hall resistance quantitatively. The fitting results yielded carrier densities and mobilities of 3:75 × 1014 cm-2 and 850 cm2·V-1·s-1, respectively, for holes, and 1.468 × 1013 cm2, 4118 cm2×V-1·s-1, respectively, for electrons, with a hole-dominant conduction at 2.5 K. Hence, an effective mobility can be achieved, which is in reasonable agreement with the effective hole mobility of 1800 cm2×V-1×s-1, extracted from the MR. Further, the angle-dependent MR, proportional to cos θ, where θ is the angle between the external magnetic field and the perpendicular orientation of the sample plane, also implies a high anisotropy of the Fermi surface. Our results about SrMnBi2 thin films, as one of a new class of AEMnBi2 and AEMnSb2 (AE = Ca, Sr, Ba, Yb, Eu) materials, suggest that they have a lot of exotic transport properties to be investigated, and that their high mobility might facilitate electronic device applications.
KeywordsSrMnBi2 thin films magnetoresistance two carriers anisotropic Dirac fermions
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