Abstract and subjects
We report significantly enhanced critical current densities (Jc) and flux pinning forces (F-p) in applied magnetic fields for YBa2Cu3O7 (YBCO) films with embedded Ba2YNbO6 (BYNO) nanorods. The films were grown by pulsed laser deposition with a target consisting of YBa(2)Cu(3)Oy with five molar per cent additions of BaNbOy and Y2O3. With this composition, deposited films were found to contain a high density of BYNO nanorods that frequently traversed the entire thickness of the film (up to 1 mu m), depending upon the deposition conditions. Enhanced Jc performance occurs primarily for applied field orientations near the c-axis of the YBCO, which is nominally along the growth direction of the BYNO nanorods. The threading nanorod density of one film of the present work was measured by plan-view transmission electron microscopy to be 710-850 nanorods mu m(-2). For approximately 1 mu m thick films, typical J(c)(75.6 K, sf) and J(c)(75.6 K, 1 T parallel to c) values were similar to 4.5 MA cm(-2) and 1.3-1.5 MA cm(-2), respectively. For a 0.5 mu m thick film, J(c)(75.6 K, 1 T parallel to c) > 2 MA cm(-2) was achieved, and values of F-p in excess of 30 and 120 GN m(-3) were achieved at 75.5 K and 65 K, respectively.