Vortex Dynamics Differences Due To Twin-boundary Pinning Anisotropy In Yba 2cu 3o X At Low Temperatures For H∥ab Planes

We measured the magnetization M of a twin-aligned single crystal of YBa 2Cu 3O x (YBaCuO), with T c =91 K, as a function of temperature T and magnetic field H, with H applied along the ab planes. Isothermal M-vs-H and M-vs-time curves were obtained with H applied parallel (∥) and perpendicular (⊥) to the twin boundary (TB) direction. M-vs-H curves exhibited two minima below 38 K, which resembled similar curves that have been obtained in YBaCuO for H∥c axis. Above 12 K, the field positions of the minima for H∥TB and H⊥TB were quite similar. Below 12 K, the position of the second minimum H min occurred at a higher field value with H∥TB. Below 6 K, only one minimum appeared for both field directions. At low temperatures, these minima in the M-vs-H curves produced maxima in the critical current. It was determined that vortex lines were expelled more easily for H∥TB than for H⊥TB and, therefore, below a certain field value, that J c(H⊥TB) was larger than J c(H∥TB). At T<12 K with H∥TB, the relaxation rate for flux lines leaving the crystal was found to be different from that for flux entering the crystal. We also observed flux jumps at low temperatures, with their sizes depending on the orientation of magnetic field with respect to the TB's. © 2005 The American Physical Society.712Sarikaya, M., Stern, E.A., (1988) Phys. Rev. B, 37, p. 9373Van Bakel, G.P.E.M., Hof, P.A., Van Engelen, J.P.M., Bronsveld, P.M., De Hosson, J.Th.M., (1990) Phys. Rev. B, 41, p. 9502Liu, J.Z., Jia, Y.X., Shelton, R.N., Fluss, M.J., (1991) Phys. Rev. Lett., 66, p. 1354Swartzendruber, L.J., Roitburd, A., Kaiser, D.L., Gayle, F.W., Bennett, L.H., (1990) Phys. Rev. Lett., 64, p. 483Kwok, W.K., Welp, U., Crabtree, G.W., Vandervoort, K.G., Hulscher, R., Liu, J.Z., (1990) Phys. Rev. Lett., 64, p. 966Duran, C.A., Gammel, P.L., Wolfe, R., Fratello, V.J., Bishop, D.J., Rice, J.P., Ginsberg, D.M., (1992) Nature (London), 357, p. 474Gyorgy, E.M., Van Dover, R.B., Schneemeyer, L.F., White, A.E., O'Bryan, H.M., Felder, R.J., Waszczak, J.V., Rhodes, W.W., (1990) Appl. Phys. Lett., 56, p. 2465Oussena, M., De Groot, P.A.J., Porter, S.J., Gagnon, R., Taillefer, L., (1995) Phys. Rev. B, 51, p. 1389Oussena, M., De Groot, P.A.J., Deligiannis, K., Volkozub, A.V., Gagnon, R., Taillefer, L., (1996) Phys. Rev. Lett., 76, p. 2559Vlasko-Vlasov, V.K., Dorosinskii, L.A., Polyanskii, A.A., Nikitenko, V.I., Welp, U., Veal, B.W., Crabtree, G.W., (1994) Phys. Rev. Lett., 72, p. 3246Wijngaarden, R.J., Griessen, R., Fendrich, J., Kwok, W.K., (1997) Phys. Rev. B, 55, p. 3268Duran, C.A., Gammel, P.L., Bishop, D.J., Rice, J.P., Ginsberg, D.M., (1995) Phys. Rev. Lett., 74, p. 3712Pastoriza, H., Candia, S., Nieva, G., (1999) Phys. Rev. Lett., 83, p. 1026Herbsommer, J.A., Nieva, G., Luzuriaga, J., (2000) Phys. Rev. B, 62, p. 3534Jorge, G.A., Rodriguez, E., (2000) Phys. Rev. B, 61, p. 103Bondareko, A.V., (2001) Low Temp. Phys., 27, p. 339(2001) Phys. Rev. B, 27, p. 201Esquinazi, P., Setzer, A., Fuchs, D., Kopelevich, Y., Zeldov, E., Assmann, C., (1999) Phys. Rev. B, 60, p. 12454Mints, R.G., Brandt, E.H., (1996) Phys. Rev. B, 54, p. 12421Muller, K.-H., Andrikidis, C., (1994) Phys. Rev. B, 49, p. 1294Guillot, M., Potel, M., Gougeon, P., Noel, H., Levet, J.C., Chouteau, G., Tholence, J.L., (1988) Phys. Lett. A, 127, p. 363Salem-Sugui Jr., S., Alvarenga, A.D., Friesen, M., Veal, B., Paulikas, P., (2001) Phys. Rev. B, 63, p. 216502Bean, C.P., (1962) Phys. Rev. Lett., 8, p. 250Tinkham, M., (1996) Introduction to Superconductivity, 2nd Ed., , McGraw-Hill, New YorkDe Andrade, M.C., Dilley, N.R., Ruess, F., Maple, M.B., (1998) Phys. Rev. B, 57, pp. R708Abulafia, Y., Shaulov, A., Wolfus, Y., Prozorov, R., Burlachkov, L., Yeshurun, Y., Majer, D., Vinokur, V.M., (1995) Phys. Rev. Lett., 75, p. 2404Maley, M.P., Willis, J.O., Lessure, H., McHenry, M.E., (1990) Phys. Rev. B, 42, p. 2639Shi, D., Salem-Sugui Jr., S., (1991) Phys. Rev. B, 44, p. 7647Beasley, M.R., Labash, R., Weeb, W.W., (1969) Phys. Rev., 181, p. 682Burlachkov, L., (1993) Phys. Rev. B, 47, p. 8056Alvarenga, A.D., Salem-Sugui Jr., S., (1994) Physica C, 235, p. 2811Junod, A., (1989) Physica C, 162-164, p. 482Triscone, G., (1990) Physica C, 168, p. 40Genoud, J.Y., (1991) Physica C, 177, p. 31

Investigations of flux pinning and creep in high-T_c superconductors

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Lowest Landau Level Diamagnetic Fluctuations In Niobium

We have performed a magnetic study of a bulk metallic sample of Nb with critical temerature Tc=8.5 K. Magnetization measurement taken for magnetic fields greater than 1 kOe show a superconducting transition that becomes broader as the field is increased. The data are well described by lowest Landau level (LLL) fluctuation theory. A scaling analysis yields values for the supercondunting transition temperature under field Tc(H) which are consistent with Hc2(T). © 2004 Published by Elsevier B.V.408-4101-4664665Bergmann, G., (1969) Z. Phys., 225, p. 430Lee, P.A., Shenoy, S.R., (1972) Phys. Rev. Lett., 28, p. 1025Ullah, S., Dorsey, A.T., (1990) Phys. Rev. Lett., 65, p. 2066(1991) Phys. Rev. B, 44, p. 262Welp, U., (1991) Phys. Rev. Lett., 67, p. 3180Suenaga, M., (1991) Phys. Rev. Lett., 66, p. 1777Tinkham, M., (1996) Introduction to Superconductivity, Second Ed., , McGraw-Hill, New YorkFarrant, S.P., Gough, C.E., (1975) Phys. Rev. Lett., 34, p. 943Salem-Sugui Jr., S., Da Silva, E.Z., (1994) Phisica C, 235, p. 1919Salem-Sugui Jr., S., (2002) Phys. Rev. B, 66. , art. 13452