Effect of inclined columnar defects on flux lines pinning in Pb-substituted Bi 2Sr 2Ca 1Cu 2O 8 single crystals

Abstract

Current–voltage characteristics are investigated in Bi 1.8Pb 0.2Sr 2CaCu 2O 8+ δ single crystals irradiated by high-energy heavy-ions parallel and along the direction tilted by 45° from to the c-axis. The angular dependence of the resistance exhibits, in the vortex solid state and for T≥40 K, a usual unidirectional effect when a magnetic field is aligned to the columnar defects (CDs) for both samples. In the case of inclined defects two dips are available: one in the direction parallel to the tracks and the other perpendicularly. The melting transition for magnetic field applied parallely to the CDs and over a wide filling factor ( f< H/ B φ ) ranging from 0.026 to 0.9, is analysed by current–voltage ( I– V) characteristics scaling: both samples show a three-dimensional Bose-glass (BG) transition with the same critical exponents ( z′=5.27±0.05 and ν′=1.04±0.06). These results support the persistence of the BG to liquid transition at T BG( B) in the case of inclined CDs.