J. Phys. I France 3 (1993) 863-870
Field and temperature dependence of the mean penetration rate of fluxons in the mixed state of high- superconductorsMitsuru Uehara1 and Bernard Barbara2
1 National Research Institute For Metals, 1-2-1, Sengen Tsukuba, Ibaraki-305, Japan
2 Laboratoire Louis Néel, CNRS, 166X, 38042 Grenoble Cedex, France
(Received 12 November 1991, revised 9 October 1992, accepted 15 October 1992)
The time decay of the zero field cooled diamagnetic magnetization of superconducting Bi(Pb) 2Sr 2Ca 2Cu 3O and YBa 2Cu 3O ceramics has been measured and analyzed in terms of a mean activation energy . We find where is the thermodynamic critical field, H the applied one and H0 a constant. The proportionality coefficient as well as the characteristic field H0, depend sensitively on the level of diamagnetic susceptibility at which experiments are performed. Our experiments show below 10 K the existence of an anomaly on the mean activation energy. Different possible alternatives to explain this phenomenon are considered, the most probable being a (thermally assisted) quantum tunneling of vortex lines.
74.30C - 74.60J - 74.60G
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