A comparative study was made of 2 thin films grown using different techniques. The critical current density at different temperatures and magnetic fields was evaluated from magnetization curves, the structure of the superconducting order parameter was obtained from point-contact spectroscopy and the scattering rates were evaluated by fitting the temperature dependent normal-state resistivity to the 2-band model. The films had similar critical temperatures close to 39K, but the upper critical fields were different by a factor of 2 (5.2 and 2.5T at 20K). It was found that the film with higher HC2 also had stronger scattering in the σ band and a smaller value of the superconducting gap in this band. As the scattering in the σ band was primarily due to the defects in the B plane, the results were consistent with the assumption that disordering the B planes led to enhanced HC2 and better pinning properties in a magnetic field.

Superconducting Gap Structure and Pinning in Disordered MgB2 Films. Y.Bugoslavsky, Y.Miyoshi, G.K.Perkins, A.D.Caplin, L.F.Cohen, H.Y.Zhai, H.M.Christen, A.V.Pogrebnyakov, X.X.Xi, O.V.Dolgov: Superconductor Science and Technology, 2004, 17, S350-4