Optical Constants of Sputtered Ferrite Films

Abstract

Transmission and reflection spectra in the 250–50 000 cm−1 region have been obtained for nickel and cobalt ferrite films deposited by d.c. sputtering of the polycrystalline ferrites onto glass and fused-silica substrates. Both types of films exhibit an absorption edge at 14 000 cm−1.From interference effects in the films, dispersion curves have been obtained in the 4000–16 000 cm−1 range by a method which compensates for the absorption effects. In this region, the absorption coefficients were obtained from the dispersion curves and the transmission spectra. The results indicate that the films may be inhomogeneous. The refractive indices of nickel ferrite films 1000 and 23 600 Å thick are 2.7 and 2.1 respectively. A method for determining the optical constants from the reflectance and transmittance at higher frequencies was also investigated.