TEMPERATURE-RANGE FOR CRITICAL SCALING BEHAVIOR IN YBCO THIN-FILMS

The magnetic and transport properties of thin films and single crystals of YBa2Cu3O7-delta are compared. For measurements on thin films, the apparent critical scaling behavior is observed to exist over a temperature range from 87 K down to the vortex-glass transition T(g) = 84.2 K at 2.5 kOE and from 83 K to T(g) = 70.4 K at 50 kOe. The inflection point (T(int)) in temperature dependent resistivity measurements R(T) coincides with the highest temperature at which current-voltage (I-V) characteristics are found to scale. The region between T(g) and T(inf) shows a behavior characteristic of thermally activated flux motion, while above T(inf) I-V curves show ohmic behavior. No similar scaling region is observed in some single crystal results, supporting recent claims that the phase transition in some single crystals may not be critical in nature (of order greater than one).