Anomalous field dependence of the critical current and flux creep rate in Pb/Ge multilayers

✍ Scribed by M. Baert; V.V. Metlushko; K. Temst; E. Rosseel; C.D. Potter; J. Snauwaert; L. Hellemans; V.V. Moshchalkov; Y. Bruynseraede

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 472 KB
• Volume: 228
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(94)90171-6

✦ Synopsis

Critical current densities J~ and normalized flux creep rate S(-dlnM/dln t) have been measured as a function oi the perpendicular field HI in low-To Pb/Ge multilayers, which can be used to model the superconducting properties of the layered high-T~ cuprates. By taking a proper Ge separator thickness a field-induced crossover between two different pinning regimes can be observed. This transition leads to an anomalous behavior ofJJHl ) and S(Ha ) in Pb/Ge multilayers, while a single Pb film demonstrates a monotonic suppression of J~ by H ~. These data have been analyzed in the framework of the collectivc pinning (CP) theory of magnetically coupled superconducting planes: the JJH±) anomaly is interpreted as a crossover from three-dimensional (3D) flux lines in low fields to two-dimensional (2D) pancake vortices in higher fields. This interpretation has also been confirmed by the suppression of the JJH •) anomaly in the Pb/Ge multilayers with a square lattice of holes, forming additional defects for the confinement of the flux lines and for the expansion of the 3D regime.