Flux pinning effects of Y2O3 nanoparticulate dispersions in multilayered YBCO thin films

The flux pinning effects of Y2O3 nanoparticulate inclusions in YBa2Cu3O7−δ (Y123 or YBCO) thin films using (Y2O3/Y123) × N multilayer structures were studied. The multilayer films were made with pulsed laser deposition (PLD) on SrTiO3 and LaAlO3 substrates with a Y2O3 nanoparticulate 'pseudo-layer' thickness ranging from 0.2 to 1.4 nm, and YBCO layer thickness varying from 7 to 50 nm. Scanning electron microscopy images showed well-defined nanoparticle formation on film surfaces, with an approximate number density of (0.8-1.6) × 1011 particles/cm2 depending on Y2O3 thickness. Minor reductions in the critical temperature (Tc) were measured for each increase in Y2O3 pseudo-layer thickness. Transport critical currents (77 K, self-field) of 3-5 MA/cm2 were consistently achieved for composite films with ⩽0.6 nm Y2O3 pseudo-layer thicknesses. Magnetic Jc measurements using vibrating sample magnetometry (H ⩽ 9 T, @70 and 77 K) showed a degradation of film properties for Y2O3 pseudo-layer thickness greater than 0.6 nm. A comparison to Y211/Y123 multilayer films showed the thinner Y2O3 pseudo-layer films exhibited similar properties.