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 to 300 cm(-1) and 4.2 to 350K. A number of infrared active modes between 20- 150 cm(-1) have been observed. Some of these modes such as 68, 72, 82, 103 cm(-1) are consist with the earlier reports by inelastic neutron scattering method and characterized as transverse acoustic phonon modes. Our measurements also shows extra modes such as 35, 44, 56, 75, 82 cm(-1). The spectra in the far-infrared region has about 60% transmission at 4.2K and opaque above 180cm(-1). The transparent properties of single crystal MgAl2O4 in fat infrared region in liquid helium temperature is especially good for HTSC thin films substrate.