Critical current densities JC of MgB2 thin films were measured. The latter were prepared by electron beam evaporation, without any post-annealing. In order to improve the characteristics of JC in high magnetic fields, a MgB2 thin film was deposited in an O2 atmosphere. The values of JC of the O2-doped film exceeded those of non-doped films in magnetic fields applied perpendicular or parallel to the c-axis. A peak in JC caused by c-axis correlated pinning centers was observed in the angular dependence of JC. The upper critical field BC2 and the vortex glass–liquid transition field Bg were estimated from temperature dependences of resistivity curves in both directions of the magnetic fields; perpendicular and parallel to the c-axis. It was found that BC2 and Bg were increased by the introduction of O2 in both the directions of the applied field. This fact indicates that effective pinning centers were introduced by the deposition of the MgB2 thin film in an O2 atmosphere.

Critical Current Density of MgB2 Thin Film with Pinning Centres Introduced by Deposition in Oxygen Atmosphere. M.Haruta, T.Fujiyoshi, T.Sueyoshi, K.Miyahara, T.Doi, H.Kitaguchi, S.Awaji, K.Watanabe: Superconductor Science and Technology, 2005, 18, 1460-3