Critical current properties under high magnetic fields up to 30 T for Y-Ba-Cu-O films by MOCVD

Y-Ba-Cu-O superconducting film prepared by MOCVD (metalorganic chemical vapor deposition) was shown to have excellent critical current density of 2.7*10/sup 6/ A/cm/sup 2/ at 77 K, 0 T and 2.5*10/sup 4/ cm/2 at 77 K, 30 T respectively. The upper critical field, B/sub c2/, for the film was estimated to be 59 T at 77 K. The activation energy U/sub 0/(B), of 1.98 eV at 21 T was determined by electrical resistance measurement under magnetic fields. The Cu composition of the film was approximately 75% over from the stoichiometry of YBa/sub 2/Cu/sub 3/O/sub 7-x/ system. The J/sub c/ properties under high magnetic fields strongly depended on the Cu composition of the films. The optimum value of Cu ratio for obtaining the highest J/sub c/ was about 5.2.