Matching effect between the density of screw dislocations and the break field in the irreversibility lines of YBa2Cu3O7−δ films

✍ Scribed by T. Ishida; K. Okuda; K. Hirata; H.P. Lang; H.-J. Güntherodt

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 678 KB
• Volume: 266
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(96)00348-6

✦ Synopsis

We have investigated the effect of screw dislocations on the irreversibility lines of Y-Ba-Cu-O films. The density n~ of screw dislocations is controlled between 2.0 × 1013 and 7.9 x 1013 m -2 by a subtle change in stoichiometry. We employ a nonlinearity criterion using the harmonic susceptibility to determine the irreversibility line, where the AC field amplitude /zoHAc (/Xo = 4~" × 10 -7 H/m) is fixed at 0.I mT while the DC magnetic field/zoHoc varies up to 1 T. We have found a step-wise anomalous change in the irreversibility lines. A break field p~oH~k, where the steep change starts as a function of decreasing field, is proportional to the pinning capability of screw dislocations B~ =/zo~b0nsd (~bo is the flux quantum). The frequency dependence of the irreversibility temperature is also discussed.