Top-down and bottom-up through-thickness current anisotropy in a bilayer YBa2Cu3O7−x film

The authors find the critical current anisotropy of a bilayer YBa2Cu3O7−δ film with different pinning structures in each layer is the sum of the anisotropy of the two individual layers, revealing that it is possible to tune the anisotropy of the composite through variation of an individual layer’s thickness and pinning structure. YBa2Cu4Ox intergrowths and Dy2O3 nanodots were the dominant pinning structures in the top and bottom layers, respectively. The bottom layer of the composite was isolated using traditional Ar+ ion milling and the top layer was isolated using a focused ion beam, allowing each layer to be studied independently.