Comparison of ac susceptibility of YBa2Cu3O7 coated conductors and single crystals

The complex ac susceptibility of YBa2Cu3O7 (YBCO) coated conductor and YBCO single crystal has been measured at 77 K as a function of field amplitude and frequency, from which the E(J) characteristic is deduced. It is shown that the E(J) in the single crystal obeys a power law in a large range above E-c=1 muV/cm, indicating a flux creep mechanism, whereas for the coated conductor there appears a transition from flux creep to flux flow at Esimilar to10E(c). The reported contactless technique may be conveniently used for the research and development of coated conductors. (C) 2004 American Institute of Physics.