Critical current density of MgB₂thin film with pinning centres introduced by deposition in oxygen atmosphere

Abstract

Critical current densities Jc of MgB2 thin films have been measured; these were prepared by an electron beam evaporation method 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 have exceeded those of the non-doped film in magnetic fields applied perpendicular and also parallel to the c-axis. The peak of Jc caused by the c-axis correlated pinning centres has been observed in the angular dependence of Jc. The upper critical field Bc2 and the vortex glass–liquid transition field Bg have been estimated from temperature dependences of resistivity curves in both directions of the magnetic fields perpendicular and parallel to the c-axis. It is found that Bc2 and Bg are increased by the introduction of O2 in both the directions of the applied field. This fact indicates that effective pinning centres have been introduced by the deposition of the MgB2 thin film in an O2 atmosphere.