Devices based on the structural and transport anisotropy in NdBa₂Cu₃O₇ thin films deposited by pulsed laser ablation on SrTiO₃ [0 0 1]

We have made high quality c-axis NdBa₂Cu₃O₇ thin films on [0 0 1] SrTiO₃ by pulsed laser deposition, with much better crystalline properties than YBa₂Cu₃O₇: smooth surface and low outgrowth density. TEM and 4-circle X-ray diffraction experiments reveal only a single orientation of the twins [1 1 0], as opposed to YBCO where both [1 1 0] and [1 1̄ 0] twin orientations are observed. This anisotropy is consistently observed by critical current measurements and magneto-optical microscopy in the superconducting state. Anisotropy in magnetic field penetration is attributed to the anisotropic twinning rate along the [1 1 0] and [1 1̄ 0] directions which is 0/1 in NdBa₂Cu₃O₇ films, whereas it is close to 0.5/0.5 for YBa₂Cu₃O₇ deposited on [0 0 1] SrTiO₃. We present devices requiring such features as vortex mobility or periodic pinning of the vortices.