Nonlinear electrodynamics in the granular superconductor YBa/sub 2/Cu/sub 3/O/sub 7/: Experiments and interpretation
For bulk samples of superconducting YBa/sub 2/Cu/sub 3/O/sub 7/ powder and pellets subject to a dc magnetic field /ital H//sub 0/ and a parallel ac magnetic field /ital H//sub 1/ at frequency /ital f/approx.10/sup 3/ to 10/sup 5/ Hz, we report data on the generated harmonic power /ital P/(/ital nf/) up to harmonic /ital n/approx.40, finding: (1) If /ital H//sub 0/=0, only odd harmonics; (2) if /ital H//sub 0//ne/0, even harmonics are additionally generated; (3) for /ital H//sub 1/ sufficiently large (/approx gt/10 Oe) and /ital n/ large, then /ital P/(/ital nf/) vs /ital H//sub 0/ displays sharp and deep periodic dips, revealing a remarkably consistent and reproducible macroscopic flux quantization for the bulk sample. These data, as well as the relative intensities of the harmonic power, are found to be in semiquantitative agreement with detailed numerical predictions of a dynamical model of the material as a suitably averaged ensemble of prototype flux quantized loops with weak links. At lower values of /ital H//sub 1/ additional structure is observed, related to fluxon pinning and depinning.
- Research Organization:
- Physics Department, University of California, Berkeley, California 94720(US); Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720; Calvin Laboratory, Lawrence Berkeley Laboratory, Berkeley, California 94720
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6258245
- Journal Information:
- Phys. Rev. B: Condens. Matter; (United States), Vol. 39:16
- Country of Publication:
- United States
- Language:
- English
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SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM OXIDES
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GRANULAR MATERIALS
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