A comparative study on the flux pinning properties of Zr-doped YBCO film with those of Sn-doped one prepared by metal-organic deposition

Abstract

We investigated the flux pinning properties of both 10 mol% Zr-and Sn-doped <TEX>$YBa_2Cu_3O_{7-{\delta}}$</TEX> (YBCO) films with the same thickness of ~350 nm for a comparative purpose. The films were prepared on the <TEX>$SrTiO_3$</TEX> (STO) single crystal substrate by the metal-organic deposition (MOD) process. Compared with Sn-doped YBCO film, Zr-doped one exhibited a significant enhancement in the critical current density (<TEX>$J_c$</TEX>) and pinning force density (<TEX>$F_p$</TEX>). The anisotropic <TEX>$J_{c,min}/J_{c,max}$</TEX> ratio in the field-angle dependence of <TEX>$J_c$</TEX> at 77 K for 1 T was also improved from 0.23 for Sn-doped YBCO to 0.39 for Zr-doped YBCO. Thus, the highest magnetic <TEX>$J_c$</TEX> values of 9.0 and <TEX>$2.9MA/cm^2$</TEX> with the maximum <TEX>$F_p$</TEX> (<TEX>$F_{p,max}$</TEX>) values of 19 and <TEX>$5GN/m^3$</TEX> at 65 and 77 K for H // c, respectively, could be achieved from Zr-doped YBCO film. The stronger pinning effect in Zr-doped YBCO film is attributable to smaller <TEX>$BaZrO_3$</TEX> (BZO) nanoparticles (the average size <TEX>${\approx}28.4$</TEX> nm) than <TEX>$YBa_2SnO_{5.5}$</TEX> (YBSO) nanoparticles (the average size <TEX>${\approx}45.0$</TEX> nm) incorporated in Sn-doped YBCO film since smaller nanoparticles can generate more defects acting as effective flux pinning sites due to larger incoherent interfacial area for the same doping concentration.