Dielectric properties of substrates for deposition of high-T/sub c/ thin films up to 40 GHz

Dielectric properties of CaNdAlO/sub 4/, LaAlO/sub 3/, SrLaAlO/sub 4/, SrLaGa/sub 3/O/sub 7/, and NdGaO/sub 3/ monocrystals, prospective substrate materials for the deposition of thin films of high-temperature superconductors, were measured with high accuracy at frequencies up to 40 GHz in the temperature range 10 to 300 K. Most materials exhibit uniaxial anisotropy with epsilon '/sub r/ ranging from 8.88 (SrLaGa/sub 3/O/sub 7/ along optical c-axis) to 24.18 (LaAlO/sub 3/). A decrease of epsilon 'r with temperature decrease was observed in all materials CaNdAlO/sub 4/ (perpendicular to c-axis) where epsilon 'r increases. Microwave losses in LaAlO/sub 3/, SrLaAlO/sub 4/ and SrLaGa/sub 3/O/sub 7/ decrease with temperature while CaNdAlO/sub 4/ and NaGaO/sub 3/ pronounced loss increase was found at temperatures below 100 K. The authors suggest that in the latter materials at lower temperatures, neodymium ions become magnetically ordered and are responsible for the observed effects.<>