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

We study the field (H) and temperature (T) dependence of the critical current density (J(c)) and irreversibility field (H-irr) at different field orientations in Y0.77Gd0.23Ba2Cu3Oy with randomly distributed BaZrO3 nanoparticles (YGdBCO + BZO) and YBa2Cu3Oy (YBCO) films. Both MOD films have large RE2Cu2O5 (225) nanoparticles (similar to 80 nm in diameter) and a high density of twin boundaries (TB). In addition, YGdBCO + BZO films have a high density of BZO nanoparticles (similar to 25 nm in diameter). At high temperatures (T > 40 K), the superconducting properties, such as J(c), H-irr, 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 J(c) of YBCO films follow a power-law dependence (proportional to 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 shows J(c) (T, 0.01T) similar to [1 -(T/T-c)(2)](n) with n similar to 1.24 +/- 0.05, which points to "delta T-c 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 H-irr and improved J(c) 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.