We present experimental results of the upper critical fields Hc2 of various MgB2 thin films prepared by the molecular beam epitaxy, multiple-targets sputtering, and co-evaporation deposition apparatus. Experimental data of the Hc2(T ) are successfully analyzed by applying the Gurevich theory of dirty two-band superconductivity in the case of Dπ/Dσ > 1, where Dπ and Dσ are the intraband electron diffusivities for π and σ bands, respectively. We find that the parameters obtained from the analysis are strongly correlated to the superconducting transition temperature Tc of the films. We also discuss the anormalous narrowing of the transition width at intermediate temperatures confirmed by the magnetoresistance measurements.

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