Magneto-Optical Kerr Effects of Nd-(Fe, Co) Thin Films

The contribution of Nd to the magneto-optical properties of vacuum-evaporated Nd-(Fe, Co) films has been investigated by measuring the wavelength dependence (for λ=250 to 800 nm) of the Kerr rotation (θ_K), together with the spectra of photoelectrons emitted under X-ray irradiation (XPS). The Kerr rotation in Nd-Co films increases with decreasing λ when the Nd concentration is over 14 at%, and shows peaks at 300 nm; while the Kerr spectra of Nd-Fe films levels off with increasing Nd content. The compositional dependence of the Kerr spectra of Nd-Co and Nd-Fe films is characterized by two factors: 1) the contribution of Nd to θ_K at short wavelengths, and 2) the differences in the Kerr spectra of crystalline and amorphous states of Co and Fe. The XPS intensity for Nd-Co and Nd-Fe is maximum at about 4.2 eV below the Fermi level, which corresponds to the peak in the θ_K spectra at 300 nm. In pseudobinary system Nd-(Fe,Co) films, λ_K is larger, over the entire range of wavelengths considered, than any other binary system with the same Nd composition; and Nd₂₂ (Fe₆₅ Co₃₅)₇₈ exhibits a θ_K of about 0.58° at 300 nm.