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|Type:||Artigo de periódico|
|Title:||Vortex Dynamics Differences Due To Twin-boundary Pinning Anisotropy In Yba 2cu 3o X At Low Temperatures For H∥ab Planes|
|Author:||Salem-Sugui Jr. S.|
|Abstract:||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.|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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