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Re-entrant behavior of low-field flux creep in c-axis-oriented HgBa2CaCu2O6+delta thin films
KTH, Superseded Departments, Materials Science and Engineering.
2001 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 6418, no 18Article in journal (Refereed) Published
Abstract [en]

The temperature, ac and dc field, and current dependent activation energy U(T,H)[(J(c0)/J(c))(mu)-1]/mu governing low-field flux creep in epitaxial c-axis-oriented HgBa2CaCu2O6+delta thin films has been determined from measurements of the frequency-dependent in-phase ac susceptibility. Above 35 K three different thermally activated flux creep regimes can be identified: (i) dislocation-mediated plastic flux creep, described by U(T,H) = U-0(1 - t(4))H-1/2 and mu = 0, (ii) elastic collective flux creep which decreases with temperature and has a weaker field dependence of H-0.22 above a field-dependent temperature Tc.(H) where A acquires finite values, and (iii) reappearance of dislocation-mediated plastic flux creep which rapidly increases as T-c is approached. It is argued that the re-entrant plastic-elastic-plastic vortex creep behavior is driven by the underlying temperature and field dependence of the shear modulus c(66). T-cm(H) marks a line in the H-T plane where the increasing c(66) promotes long-range correlations in the dilute vortex phase and creep becomes collective. At high H and T, c(66) again decreases and plastic creep reappears as the ordered phase starts to melt. Evidence for thermally assisted quantum creep is observed up to temperatures as high as T-0 = 35 K.

Place, publisher, year, edition, pages
2001. Vol. 6418, no 18
Keyword [en]
high-tc superconductors, high-temperature superconductors, quantum collective creep, single-crystal, ac susceptibility, vortex-lattice, layered superconductors, thermal fluctuations, ii superconductors, activation-energy
URN: urn:nbn:se:kth:diva-21108ISI: 000172239400116OAI: diva2:339805
QC 20100525Available from: 2010-08-10 Created: 2010-08-10Bibliographically approved

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