Strong enhancement of flux pinning in thick NdBa2 Cu3 O7-δ films grown on ion-beam assisted deposition-MgO templates via three-dimensional self-assembled stacks of BaZrO3 nanodots

Thick, epitaxial NdBa2 Cu3 O7-δ (NdBCO) films (up to 2.1 μm) with a high density of nanoscale columnar defects parallel to the c -axis of the film were deposited on ion-beam assisted deposition-MgO templates via pulsed laser deposition. The columnar defects were composed of self-assembled BaZrO3 (BZO) nanodots. A significant enhancement in Jc for Hc is found for these films. In addition, an overall improvement in the in-field Jc at all field orientations is observed. Compared to pure NdBCO of similar thickness, the in-field Jc at Hc for 0.7 μm thick NdBCO+BZO film is improved by a factor of 2-4 in the field range of 0.1-4 T and 10-20 at 7-8 T at 77 K. In addition, a smaller α∼0.17 is found in the field regime where Jc ∼ H-α. Also, a higher maximum pinning force, Fp max ∼14 GN m3, is found at 3 T and a larger Hirr over 8 T is found for the NdBCO films with columnar defects.