2008 年 43 巻 8 号 p. 360-364
Flux pinning properties of multilayered MgB2/Ni thin film prepared by an electron beam evaporation method were investigated. The MgB2/Ni thin film shows the peak around the matching magnetic field in the magnetic field dependence of Jc when the magnetic field is applied in the direction parallel to the surface of the thin film. The strong peak also appears at the B // surface in the field angular dependence of Jc. These results indicate that Ni layers work as two-dimensional pinning centers. Electric field vs. current density characteristics were measured in various magnetic fields and temperatures to obtain the vortex glass-liquid transition temperature Tg and the m-value. The value of Tg at the B // surface was much larger than that of Tg at the B ⊥ surface. The magnetic field dependence of m-value changes drastically at the matching magnetic field when the magnetic field is applied in the direction parallel to the thin-film surface.