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 2.7×10⁶ A/cm² at 77 K, 0 T and 2.5×10⁴ cm/2 at 77 K, 30 T respectively. The upper critical field, B_c2, for the film was estimated to be 59 T at 77 K. The activation energy U₀(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 YBa₂Cu₃O_7-x system. The J_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_c was about 5.2