Transport and magnetic properties of high- Tc YBa sub 2 Cu sub 3 O sub 7 minus x films

Thin superconducting films of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} were deposited onto (100) SrTiO{sub 3} substrates at 750 {degree}C in 100 and 200 mTorr of O{sub 2}, by ArF excimer laser ablation. The as-deposited films were strongly oriented with the {ital c} axis perpendicular to the surface when they were cooled to room temperature in oxygen. The highest values of transport critical current density ({ital J}{sub {ital c}}{gt}10{sup 5} A/cm{sup 2} below 80 K) were observed in films cooled in flowing O{sub 2}. We find that, in all films, {ital J}{sub {ital c}} follows a power law (1{minus}{ital T}/{Tc}){sup {ital n}} with {ital n}{approx}2, near the critical temperature, {Tc}, when {Tc} is defined as the temperature at which {ital J}{sub {ital c}}=0. It appears that this behavior is governed by the short coherence lengths in this high-{Tc} material, as suggested by G. Deutscher and K. A. Mueller (Phys. Rev. Lett. {bold 59}, 1745 (1987)), and not by the specific nature of the large-scale structure of the films.