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In order to achieve high magnetic field in superconducting magnet, superconducting tape conductor with effective pinning centers is required for high critical current density. We studied periodic artificial pinning centers for the scope of use in HTS tape conductor. Periodic patterns were introduced as artificial pinning centers on a superconducting Nb film. To investigate the effect of flux pinning, 2 and 4 m period groove patterns were formed on the Nb film with various depths. Magnetization and critical current density of the films with the groove patterns were larger than those of the film without the pattern, as a result of effective artificial pinning. After regarding immanent magnetization caused by defects, films with 2 m period grooves had about 2 times as much increase of magnetization as the films with 4 m period grooves. Ratio of pinning force density of 2 m period groove pattern to that of 4 m period groove pattern was calculated to be 2, and we found this calculated value is in good agreement with the experimental one. The magnetization of both films increased with groove depth until that reached a half of film thickness. It is considered that this increase of magnetization with groove depth is mainly caused by an increase of elementary pinning force for individual flux line.

Ag added bulk FeSe 0.5 Te 0.5 single crystal like samples Ag x (FeSe 0.5 Te 0.5 ) 1x were prepared by solidstate reaction. The x, nominal concentration of Ag, was ranged between 0 and 8%. The pure Ag or Ag compound was not observed in the Xray diffraction patterns of Ag doped samples. The temperature and magnetic field dependences of magnetizations of prepared samples were measured using a superconducting quantum interference device (SQUID) magnetometer. The T c was about 14K up to x=4%, but the T c decreased gradually to 11K above x=5%. The calculated lattice parameter a is approximately constant with Ag addition. On the other hand, the c is nearly constant in the sample of x≤5%, but it decreases rapidly in x≥6%. The x dependence of T c corresponds to the lattice parameter c. It means that, Ag might replace Fe and partially distorts a tetragonal FeSe 0.5 Te 0.5 crystal structure in x>6%. The magnetization decreased with increasing of x, but the fishtaillike humps were observed in the magnetization curves. The maximal J c (x)/J c (0) was about 1.5 at x=5% and 5T under the applied magnetic field H perpendicular to the caxis. The pinning potentials (U 0 ) were estimated from relaxation measurement of the magnetization at 5K when H was parallel to the caxis. As a result, the sample of x=5% is considered to be more susceptible to flux creep than the sample of x=0%.