Microwave compatible YBa2Cu3O7−x films on ferrimagnetic garnet substrates

Abstract

High quality epitaxial YBa2Cu3O7−x (YBCO) thin films have been deposited onto ferrimagnetic yttrium iron garnet (100) substrates using a double buffer layer lattice engineering scheme. The YBCO films are c-axis oriented and show superconductive transition temperatures of 88–89 K with transition widths ≤0.5 K. The films also exhibited Jc’s of 2.7×106 A/cm2 in zero field and 1.1 ×106 A/cm2 in 2000 G at 77 K. Dielectric resonator measurements indicated unloaded Q values of 29 000 at 77 K and 24 GHz for unpatterned films. These values correspond to a surface resistance (RS) of 500 μΩ at 77 K, 10 GHz, which is the lowest obtained to date for a YBCO film on a ferrimagnetic substrate. Such films could be used for fabricating miniature-high-temperature superconducting microwave elements such as nonreciprocal and passive microwave devices, making possible, their integration on a single ferrimagnetic wafer.