Enhancement of Tc in YBa2Cu3O7 by chemical substitution in bulk and thin film materials: Implications for the upper critical magnetic field

Abstract

Chemical substitution of La +3 for Ba +2 in compounds of composition YBa 2−x La x Cu 3 O 7−gd is shown to increase the superconducting transition temperature T c by ∼ 2 K and the electrical resistivity π(100 K) by 90% for x=0.06. The increase of T c is argued to result from a reduction of the hole carrier density. These results lead to the speculation that the upper critical magnetic field H c 2 may be increased by as much as 50% through this simple subsitution. Thin films prepared by pulsed-laser deposition with x=0.04 and 0.06 are shown to yield T c =90.8 K.