Thermoactivated flux creep in high-temperature-superconducting rings in a low-frequency magnetic field
E. V. Matizen, P. P. Bezverkhy, V. G. Martynets, S. M. Ishikaev
DOI 10.1103/PhysRevB.59.9649 · Physical Review B
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Abstract
The effect of ac/dc magnetic fields and temperature on the trapped flux has been studied on superconducting rings, in which a random net of Josephson junctions has been established. Using the obtained experimental data, the dependences of the flux relaxation rate on temperature and magnetic field have been derived, and the flux-creep activation barrier has been evaluated. The electrodynamic properties of the samples have been calculated under three models of voltage-current characteristics under the assumption of a thin ring. When placed in an ac magnetic field and in the critical state, the ring displays a quasi-Meissner behavior, which has been verified by experiments. If ac/dc magnetic fields and temperature produce vortex density gradients throughout the ring, the flux locks up in the ring hole and stays invariable, while elsewhere in the ring creep continues. A peculiar graded decrease in the magnitude of the trapped flux has been observed under the action of ac field and has been supported by theoretical calculations; we suppose that this rapid dropoff can be accounted for by a change in effective time scale in the logarithmic creep law.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Bi1.6Pb0.4Sr2Ca2Cu3Oy Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 105 | Pressure not reported | onset |
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