Critical current density of MgB2 thin IMP films and the effect of interface pinning

Preferentially oriented MgB2 thin films with c-axis normal to the surface have been prepared and characterized for microstructure and transport properties. The magnetic field dependence of superconducting critical current density J(c) has been determined from the magnetization hysteresis (M-H) loops at various temperatures using the Bean's critical state model. High J(c) of these films show their potential for applications. We have also measured the angular dependences of J(c). The angular dependence is seen to be in agreement with the anisotropic Ginzburg-Landau model except that at angles close to the ab plane, increased pinning due to film-substrate interaction is observed. The angular range where interface pinning is effective has been determined by measurement of asymmetry in dissipation on reversal of current for fields applied at angles close to the ab plane.