Anisotropic magneto-optical response of metallic thin films probed by Vector-Magneto-Optical Generalized Ellipsometry

Magneto-optical generalized ellipsometry is the most general approach to characterize the magneto-optical response of materials. We extended this experimental approach to Vector-Magneto-Optical Generalized Ellipsometry (VMOGE) in the IR-UV spectral range, by constructing a generalized spectroscopic ellipsometer combined with a 3D vector magnet. VMOGE measures the upper 3 x 4 submatrix of the 4 x 4 Mueller matrix in a magnetic field of arbitrary orientation and magnitude up to 0.4 T at room temperature. Searching the best match model between experimental and calculated VMOGE data, the complex-valued magneto-optical dielectric tensor ε _MO is determined. Comparison with vector magnetometry measurements can provide the complex and anisotropic magneto-optical coupling constant Q_x, Q_y, Q_z. We have determined the wavelength dependence of the isotropic Q_x and Q_y of ferromagnetic Co, Fe, and Ni films. Besides, VMOGE is also employed to study Co nanowires with very strong anisotropic optical response. Having knowledge of the magneto-optical coupling constant Q(λ), one can design magneto-optical devices, e.g., ferromagnetic thin film and nanowire structures, with a strong magneto-optical response for a selected wavelength.