Magneto-Optical Properties of Perpendicular Magnetic 3d Transition-Metal Fluoride Films

The magneto-optical properties of Fe-F, Co-F and Ni-F films have been investigated. Films were prepared by rf sputtering using compressed powder targets of FeF₃, CoF₃ and NiF₂. The structure of films was confirmed to be amorphous, but containing small amounts of crystalline fluoride. Some of the films showed perpendicular magnetic anisotropy, high coercivity (600 to 2000 Oe), a fairly high remanence ratio (approximately 0.7), and a saturation magnetization of from 5 to 50 emu/g. Films also exhibited Faraday rotation coefficients of around 10⁴ deg/cm in the short-wavelength range, and varied smoothly with wavelength in the range 500 to 2000 nm. The optical absorption coefficient was also near 10⁴ cm^-1 in the range 400 to 1500 nm. Both the Kerr rotation angle and the reflection spectrum varied with the wavelength in the transparent films. The electronic structure of films was measured by soft X-ray spectroscopy, and was judged to be intermediate between the metallic and compound states.