Critical current density of MgB2 thin 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 evaporationmethod without any post-annealing. In order to improve the characteristics ofJc in high magneticfields, a MgB2 thin filmwas deposited in an O2 atmosphere. The values of Jc of the O2-doped film have exceeded those of the non-doped film inmagnetic fields applied perpendicular and also parallel to thec-axis. Thepeak of Jc caused by the c-axis correlated pinning centres has been observed in the angular dependence ofJc. The uppercritical field Bc2 and the vortex glass–liquid transition fieldBg have been estimated from temperature dependences of resistivity curves inboth directions of the magnetic fields perpendicular and parallel to thec-axis. It isfound that Bc2 andBg are increased bythe introduction of O2 in both the directions of the applied field. This fact indicates thateffective pinning centres have been introduced by the deposition of theMgB2 thinfilm in an O2 atmosphere.