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|Type:||Artigo de periódico|
|Title:||Vortex dynamics differences due to twin-boundary pinning anisotropy in YBa2Cu3Ox at low temperatures for H parallel to ab planes|
|Abstract:||We measured the magnetization M of a twin-aligned single crystal of YBa2Cu3Ox (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 (parallel to) and perpendicular (perpendicular to) 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 Hparallel toc axis. Above 12 K, the field positions of the minima for Hparallel toTB and Hperpendicular toTB were quite similar. Below 12 K, the position of the second minimum H-min occurred at a higher field value with Hparallel toTB. 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 Hparallel toTB than for Hperpendicular toTB and, therefore, below a certain field value, that J(c)(Hperpendicular toTB) was larger than J(c)(Hparallel toTB). At T<12 K with Hparallel toTB, 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.|
|Editor:||American Physical Soc|
|Appears in Collections:||Artigos e Materiais de Revistas Científicas - Unicamp|
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