Effect of inclined columnar defects on flux lines pinning in Pb-substituted Bi2Sr2Ca1Cu2O8 single crystals

Current–voltage characteristics are investigated in Bi1.8Pb0.2Sr2CaCu2O8+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/Bφ) 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 TBG(B) in the case of inclined CDs.