Magnetization studies were made of MgB2 superconducting thin films at 4.2–40K and 0–6T. Thin films prepared by both pulsed laser deposition and electron beam evaporation methods were investigated. In addition, both films were studied before and after heavy bombardment with 200MeV Ag ions to a dose of 1011/cm2. Variation of sweep rates during the measurement of the magnetization loop revealed the presence of flux creep in both films. The pulsed-laser deposition film, after irradiation, exhibited severe degradation of TC, critical current densities in low fields and irreversibility line, B*(T). In contrast, the EBE film exhibited a slight enhancement in TC, and nearly no change in JC(B) and the position of irreversibility line after irradiation. For both pristine films, the obtained volume pinning forces Fp versus reduced field b = B/B* exhibited good scaling for T ≤ 10K; which matched well with a theoretical curve based upon the flux line shear pinning model. The results could be interpreted in terms of grain boundaries in films acting as flux line shear channels.

Study of Magnetization and Pinning Mechanisms in MgB2 Thin Film Superconductors - Effect of Heavy Ion Irradiation. A.Gupta, H.Narayan, D.Astill, D.Kanjilal, C.Ferdeghini, M.Paranthaman, A.V.Narlikar: Superconductor Science and Technology, 2003, 16, 951-5