THE CURRENT-VOLTAGE CHARACTERISTICS OF SINGLE-CRYSTAL WHISKERS OF 2-2-1-2 BISCCO

The current-voltage characteristics of a single-crystal whisker of the 2:2:1:2 phase of bismuth strontium calcium copper oxide have been mea sured over a wide range of temperatures and magnetic fields. In low ma gnetic fields there are indications of a phase transition. In higher m agnetic fields the current-voltage characteristics obey powerful scali ng relationships. In large fields and low currents we find that the di ssipation has a number of the characteristics of the thermally activat ed flux creep (TAFC) model of Kim and Anderson, in particular the temp erature and magnetic field dependences of the barrier height obey the typical behaviour for that class of model. However, the flux-bundle pa rameters must be taken as temperature dependent. At high fields and hi gh currents the observed behaviour differs very significantly from the TAFC prediction.