C-axis oriented MgB2 thin films were synthesized on single-crystal MgO (111) substrates using chemical vapour deposition. The as-formed films revealed a sharp superconducting transition temperature of 38K with the transition width 0.2K. The temperature dependence of the upper critical magnetic field HC2(T) in the films was determined via resistivity for magnetic field H parallel and perpendicular to the c axis of the films. Using the Werthamer–Helfand–Hohenberg formula, the anisotropy ratio of the upper critical field was found to be 1.2.

Anisotropy of the Upper Critical Field in c-Axis Oriented MgB2 Thin Films. S.F.Wang, Z.Liu, Y.B.Zhu, Y.L.Zhou, Z.H.Chen, H.B.Lü, G.Z.Yang: Chinese Physics, 2004, 13, 1120-3