Investigation of the magnetic field angle dependence of resistance, irreversibility field, upper critical field and critical current density in DC sputtered Bi-2223 thin film

We measured resistivity and transport critical current density, Jc, as a function of DC magnetic field and the angle (ϕ) between the surface of the film and the magnetic field on ex-situ annealed, c-axis oriented Bi-2223 thin films fabricated by DC sputtering method. Irreversibility field (μ0Hirr) and upper critical field (μ0Hc2) were determined from the resistivity versus the applied magnetic field graph. It is observed that critical temperature (Tc), μ0Hirr,μ0Hc2 and Jc of the films strongly depend on the direction and strength of the field. While Tc of the film without magnetic field is observed to be about 102 K, it is found to decrease to 90 K (85 K) for the applied field perpendicular (parallel) to c-axis of the film. Not only were μ0Hirr(0) and μ0Hc2(0) values determined from the μ0Hirr and μ0Hc2 versus temperature graphs, respectively, but also penetration depths and coherence lengths were interpreted. Anisotropy of the film was also discussed by means of the change of irreversibility as a function of angle. Moreover at 4.2 K, Jc was observed to be 3000 A/cm2 at zero field; however, it was found to abruptly decrease to 1982 (1 1 2 0) A/cm2 under low magnetic field at ϕ=0° (ϕ=90°), which indicates that anisotropic Jc behavior of the film is intrinsic. Furthermore, we provided a theoretical analysis of the obtained results in the framework of intrinsic pinning theory of superconductors. Microstructural properties of the produced films were also reinvestigated by X-ray diffractometer (XRD) and scanning electron microscopy (SEM) measurements. XRD patterns indicate that the films are c-axis oriented based on the prominent (0 0 l) peaks. SEM images show needle-like grain structures dominate the surface morphology of the films.