Flux dynamics in a single-crystal YBa2Cu3O7−δ sample

✍ Scribed by I. Neeson; M. Paetkau; J.P. Harrison; A.N. Terentiev; Ruixing Liang; D.A. Bonn; W.N. Hardy

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 511 KB
• Volume: 243
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(95)00017-8

✦ Synopsis

Magnetic-flux dynamics in a high-quality single crystal of YBa2Cu307_ ~ has been studied with a swinging-beam experiment. At low temperature the flux is pinned and the response is determined by the magnetization; this shows an anisotropy which agrees with that expected from demagnetizing factors for the plate-like crystal. At intermediate temperature the flux becomes mobile and causes dissipation. The energy loss per cycle can be understood in terms of the Bean model, giving a critical current density that varies from ~ 106 A/cm 2 at 40 K to ~ 104 A/cm 2 at 75 K, for a field of 2 T. A few degrees below Tc the temperature dependence of the dissipation shows a sharp peak. This peak corresponds to a rapid onset of resistivity in the sample and can be identified with the phase transformation. The field-dependent phase transformation temperature agrees well with earlier results for untwinned single crystals. The phase transformation boundary depends upon the effective AC field which is evidence for non-ohmic behavior.