Irreversible behaviour of oriented grained YBa2Cu3Ox. Part 2: relaxation phenomena

Temperature dependence of the magnetic-flux penetration into disk-shapedYBa2Cu3Darhmaoui1, Jung2, Talvacchio3 et al. 1996Phys. Rev. B10020View full textAdd to dashboardCite

“…The weak temperature dependence of S in the full critical state close to T c for the disk and the ring ͓Fig. 5͑d͒ and 7͑a͔͒ is consistent with data of Keller et al 16 and Isaac et al 17 on the c-axis melt-textured YBCO at remanence after application of saturating fields along the c axis, and with Malozemoff's and Fisher's model 18 of universality in the current decay and flux creep of YBCO. Close to T c ͑over an applied temperature range of 60-85 K͒, the normalized decay rate from the maximum value of the trapped field Sϭ(1/B c )͑dB/d ln t͒ ϭkT/E 0 gives the energy barrier in the absence of flux creep E 0 independent of temperature, with an average value of 0.45 eV.…”

“…This number is very close to that reported for the c-axis-oriented melt-textured YBCO. 16,17 The measurement of the trapped field profiles at constant temperature for various stages of flux penetration into disk No. 2 confirmed that even in the early stages of flux penetration, the full critical state is reached at the disk's edge and it spreads steadily into the disk's center ͓Fig.…”

Elimination of magnetic relaxation in superconductors on approaching a ferromagnet

“…(2)), gives 1/S $ 30. This value is in agreement with known values of V/kT for melt-textured YBaCuO ceramics [10]. The ferromagnet retards the flux creep in the superconductor.…”

Field percolation and high current density in 80/20 DyBa2Cu3O7 − x/Dy2BaCuO5 bulk magnetically textured composite ceramics

“…We propose to understand the data with the following equation: . This is far away from the record high critical current value (10 6 A/cm 2 at 77 K) in neutron irradiated YBCO single crystals, [21] but much above that of epitaxial thin films [22], of grain aligned YBCO, [23] and other zone melt YBCO with also some 211 excess particles [24].…”