INFRARED PROPERTIES OF SINGLE-CRYSTAL MGAL2O4, A SUBSTRATE FOR HIGH-TEMPERATURE SUPERCONDUCTING FILMS

We study and analyze the infrared properties of single crystal MgAl2O4 , an important substrate for high-T-c superconducting films, from 10 t o 300 cm(-1) and 4.2 to 350K. A number of infrared active modes betwee n 20- 150 cm(-1) have been observed. Some of these modes such as 68, 7 2, 82, 103 cm(-1) are consist with the earlier reports by inelastic ne utron scattering method and characterized as transverse acoustic phono n modes. Our measurements also shows extra modes such as 35, 44, 56, 7 5, 82 cm(-1). The spectra in the far-infrared region has about 60% tra nsmission at 4.2K and opaque above 180cm(-1). The transparent properti es of single crystal MgAl2O4 in fat infrared region in liquid helium t emperature is especially good for HTSC thin films substrate.