Mixed pinning landscape at high temperature in nanoparticle-introduced YGdBa2Cu3Oy films grown by metal organic deposition

M. MIURA; B. MAIOROV; S. A. BAILY; N. HABERKORN; J. O. WILLIS; K. MARKEN; T. IZUMI; Y. SHIOHARA; L. CIVALE

PHYSICAL REVIEW B - CONDENSED MATTER AND MATERIALS PHYSICS

American Physical Society

Año: 2011 vol. 83 p. 184519 - 184526

0163-1829

We study the field (H) and temperature (T) dependence of the critical current density (Jc), andirreversibility field (Hirr) at different field orientations in Y0.77Gd0.23Ba2Cu3Oy with randomlydistributed BaZrO3-nanoparticles (YGdBCO+BZO) and YBa2Cu3Oy (YBCO) films. Both MOD films have large RE2Cu2O5 (225) nanoparticles (~80 nm in diameter) and a high density of twin boundaries (TB). In addition, YGdBCO+BZO films have a high density of BZO nanoparticles (~25 nm in diameter). At high temperatures (T > 40 K), the superconducting properties, such as Jc, Hirr and flux creep rates, are greatly affected by the BZO nanoparticles, while at low temperatures the superconducting properties of both the YBCO and YGdBCO+BZO films show similar field and temperature dependencies. In particular, while the Jc of YBCO films follow a power-law dependence (H-alpha) at all measured T, this dependence is only followed at low T for YGdBCO+BZO films. As a function of T, the YGdBCO+BZO film show Jc(T, 0.01T) [1-(T/Tc)2]n with n~1.24+/-0.05, which points to “delta Tc-pinning”. We analyze the role of different types of defects in the different temperature regimes and find that the strong pinning of the BZO-nanoparticles yields a higher Hirr and improved Jc along the c axis and at intermediate orientations at high T. The mixed pinning landscapes due to the presence of disorder of various dimensionalities have an important role in the improvement of in-field properties.