Flux creep and activation energies at the grain boundaries of Y-Ba-Cu-O superconductors
M. Nikolo, R. B. Goldfarb
DOI 10.1103/PhysRevB.39.6615 · Physical Review B
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Abstract
We measured the ac susceptibility of sintered Y1Ba2Cu3O7−δ pellets as a function of temperature and ac magnetic field amplitude and frequency. The imaginary part of the susceptibility χ’’ exhibits two peaks. A narrow peak is located at the critical temperature of the grains. A broad peak at lower temperature is attributed to hysteresis losses at the grain boundaries. There is a small shift in this coupling peak to higher temperature as the frequency increases from 10 to 1000 Hz. We explain the shift in terms of Anderson flux creep on a time scale of milliseconds. The shift depends on the amplitude of the measuring field. The activation energy for flux creep ranges from 11.9±1.0 eV in the zero-field limit [0.8 A mr-r1(0.01 Oe)] to 1.2±0.3 eV at 800 A m−1(10 Oe). We extrapolate our data to find the value for an intergrain decoupling field of 1–2 kA m-1 (13–25 Oe), above which flux creep presumably becomes flux flow at the grain boundaries.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| YBa2Cu3O7-δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 90 | Pressure unresolved | onset |
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