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Okazaki, Ryuji*; Konczykowski, M.*; Van der Beek, C. J.*; Kato, Tomonari*; Hashimoto, Kenichiro*; Shimozawa, Masaaki*; Shishido, Hiroaki*; Yamashita, Minoru*; Ishikado, Motoyuki; Kito, Hijiri*; et al.
Physica C, 470(Suppl.1), p.S485 - S486, 2010/12
Times Cited Count:0 Percentile:0(Physics, Applied)We report the lower critical fields measurements on Fe-based oxipnictide PrFeAsO single crystals for and -planes. To avoid the difficulty of determinations due to the flux pinning, we developed a novel method using a miniature hall-sensor array which can evaluate the local magnetic induction ai each sensor position. The hall sensor which is placed on the edge of the crystal clearly resolves the first flux penetration from the Meissner state. The temperature dependence of for is well scaled by the in-plane penetration depth and is consistent with a full-gap superconducting state. The anistropy of at low temperatures is estimated to be 3, which is much smaller than of . This indicates the multiband superconductivity, in which the active bands for superconductivity are more two-dimensional.
Van der Beek, C. J.*; Rizza, G.*; Konczykowski, M.*; Fertey, P.*; Monnet, I.*; Okazaki, Ryuji*; Kato, Tomonari*; Hashimoto, Kenichiro*; Shimozawa, Masaaki*; Shishido, Hiroaki*; et al.
Physica C, 470(Suppl.1), p.S385 - S386, 2010/12
Times Cited Count:1 Percentile:6.48(Physics, Applied)Crystalline disorder in the pnictide superconductor PrFeAsO is studied using magneto-optical visualisation of flux penetration, transmission electron microscopy, and X-ray diffraction using synchrotron radiation. Critical-state like flux distributions and the magnitude and temperature dependence of the critical current demonstrate bulk vortex pinning by oxygen vacancies at all temperatures.
Van der Beek, C. J.*; Rizza, G.*; Konczykowski, M.*; Fertey, P.*; Monnet, I.*; Klein, T.*; Okazaki, Ryuji*; Ishikado, Motoyuki; Kito, Hijiri*; Iyo, Akira*; et al.
Physical Review B, 81(17), p.174517_1 - 174517_11, 2010/05
Times Cited Count:98 Percentile:93.78(Materials Science, Multidisciplinary)Local magnetic measurements are used to quantitatively characterize heterogeneity and flux line pinning in PrFeAsO and NdFeAs(O,F)superconducting single crystals. In spite of spatial fluctuations of the critical current density on the macroscopic scale, it is shown that the major contribution comes from collective pinning of vortex lines by microscopic defects by the mean-free path fluctuation mechanism. The defect density extracted from experiment corresponds to the dopant atom density, which means that dopant atoms play an important role both in vortex pinning and in quasi-particle scattering.
Okazaki, Ryuji*; Konczykowski, M.*; Van der Beek, C. J.*; Kato, Tomonari*; Hashimoto, Kenichiro*; Shimozawa, Motoyuki*; Shishido, Hiroaki*; Yamashita, Minoru*; Ishikado, Motoyuki; Kito, Hijiri*; et al.
Physical Review B, 79(6), p.064520_1 - 064520_6, 2009/02
Times Cited Count:60 Percentile:87.75(Materials Science, Multidisciplinary)We have studied the lower critical fields H of superconducting iron oxipnictide PrFeAsO single crystals for H parallel and perpendicular to the ab-planes.
Ishikawa, Norito; Van der Beek, C. J.*; Dunlop, A.*; Jaskierowicz, G.*; Li, M.*; Kes, P. H.*; Della-Negra, S.*
Journal of the Physical Society of Japan, 73(10), p.2813 - 2821, 2004/10
Times Cited Count:2 Percentile:19.85(Physics, Multidisciplinary)By irradiating 30MeV C fullerene beam, we have produced tracks of diameter 20nm and length 200nm near the surface of single crystalline BiSrCaCuO. Both the critical current density and magnetic irreversibility line are significantly enhanced. The irradiated crystals have shown salient features of the (,) vortex phase diagram of vortex matter both of unirradiated sample, such as the first order vortex phase transition, and the exponential Bose glass line characteristic of heavy ion-irradiated crystals.