Devices based on the structural and transport anisotropy in NdBa_2Cu_3O_7 thin films deposited by pulsed laser ablation on SrTiO_3 001

摘要

We have made high quality c-axis NdBa_2Cu_3O_7 thin films on [001] SrTiO_3 by pulsed laser deposition, with much better crystalline properties than YBa_2Cu_3O_7: smooth surface and low outgrowth density. TEM and 4-circle X-ray diffraction experiments reveal only a single orientation of the twins [110], as opposed to YBCO where both [110] and [110] 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 [11 0] and [110] directions which is 0/1 in NdBa_2Cu_3O_7 films, whereas it is close to 0.5/0.5 for YBa_2Cu_3O_7 deposited on [001] SrTiO_3. We present devices requiring such features as vortex mobility or periodic pinning of the vortices.