DIELECTRIC-PROPERTIES OF SUBSTRATES FOR DEPOSITION OF HIGH-TC THIN-FILMS UP TO 40-GHZ

Dielectric properties of CaNdAlO4, LaAlO3, SrLaAlO4, SrLaGa3O7 and NdGaO3 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(r)' ranging from 8.88 (SrLaGa3O7 along optical c-axis) to 24.18 (LaAlO3). A decrease of epsilon(r)' with temperature decrease was observed in all materials except CaNdAlO4 (perpendicular to c-axis) where epsilon(r)' increases. Microwave losses in LaAlO3, SrLaAlO4 and SrLaGa3O7 decrease with temperature while CaNdAlO4 and NaGaO3 pronounced loss increase was found at temperatures below 100 K. We suggest, that in the latter materials at lower temperatures, neodymium ions become magnetically ordered and are responsible for the observed effects.