A STUDY ON THE DIELECTRIC TENSOR ELEMENTS OF MAGNETOOPTIC MATERIAL TBFE THIN-FILMS

A method is described to measure the dielectric tenser of perpendicula rly magnetized metal films overcoated with a transparent SiNx, layer t o prevent the oxidization of the TbFe thin films. We measured Delta, p si from ellipsometry to obtain the diagonal elements of the dielectric tenser. The off-diagonal elements of the dielectric tenser were also obtained by a conventional iteration method using the Kerr angle and t he ellipticity in the range of 4000 similar to 7000 Angstrom. To valid ate our dielectric tenser elements, we also measured the perpendicular reflectance, the Kerr angle, and the ellipticity of TbFe bilayer film s coated with different thicknesses of SiNx. The measured values agree well, within the experimental error, with the calculated values using our dielectric tenser elements. The optimum thickness of the SiNx lay er to maximize the figure of merit at the wavelength of the HeNe laser was 598 Angstrom.