Kinetic roughening of magnetic flux fronts in Bi ₂Sr ₂CaCu ₂O _8+δ crystals with columnar defects

Kinetic roughening analysis is utilized to investigate fingerlike flux-front patterns observed in a Bi ₂Sr ₂CaCu ₂O _8+δ single crystal incorporating columnar defects. At small-length scales, scaling exponents consistent with the Kardar-Parisi-Zhang (KPZ) model for a moving front in quenched noise (QKPZ) are found. A crossover to scaling exponents of a KPZ system, dominated by temporal noise, can be identified at a large-length scale, which increases with temperature. The induction-temperature range for which the QKPZ behavior is observed is linked to the accommodation line characterizing the crossover between dominating vortex-defects and vortex-vortex interaction regimes.