Multilayer buffer for high-temperature superconductor devices on MgO

A multilayer thin film epitaxial passivation of single crystal MgO substrates was developed. YBa2Cu3O7−x films on the buffered MgO substrates demonstrate pure c-axis orientation, absence of in-plane disoriented grains, transition temperature Tc>91K, and critical current density Jc∼5MA∕cm2 at 77.4K and were deposited in thicknesses of up to several micrometers without cracks. High-temperature superconductor multilayer flux transformers of 2μm thickness on the buffered MgO substrates demonstrated improved insulation between the superconducting layers and an increased dynamic range compared to flux transformers on SrTiO3 substrates.