| Abstract | We report anisotropic resistivity measurements on a La1.2Sr1.8Mn2O7 single crystal over a temperature T range from 2 to 400 K and in magnetic-fields H up to 14 T. For T>~218 K, the temperature dependence of the zero-field in-plane resistivity ?ab(T) obeys the adiabatic small polaron hopping mechanism, while the out-of-plane resistivity ?c(T) can be ascribed by an Arrhenius law with the same activation energy. Considering the magnetic character of the polarons and the close correlation between resistivity and magnetization, we developed a model which allows the determination of ?ab,c(H,T). The excellent agreement of the calculations with the measurements indicates that small polarons play an essential role in the electrical transport properties in the paramagnetic phase of bilayer manganites. |
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