First-principles modeling of the magneto-optical response in inhomogeneous systems

We develop an ab initio computational approach to calculate the magneto-optical Kerr effect spectra of layered and nanogranular compounds as a function of several structural and geometrical parameters: (i) composition, (ii) film thickness, and (iii) position, thickness, and number of the nonmagnetic interlayers. The case of nanoparticles in a matrix is treated within the effective-medium approximation and compared to a model (alternating composition layers approximation) that considers different compounds in a thin-film multilayered structure. The magneto-optical filter-amplifier effect of a nonmagnetic overlayer or interlayer and the dependence of the Kerr response on the specific sample composition suggest that our computational approach is a good starting point to build up structures with the desired magneto-optical characteristics and can be used to interpret experimental spectra to single out the microscopic structure and composition of the sample. The model is applied to the Mn-Ge binary system, considering both Mn5 Ge3 as a film or in a nanoparticle arrangement and Mnx Ge1-x diluted semiconductor as possible phases in pure form or intermixed with Ge.