Linear and quadratic magneto-optical Kerr effects in continuous and granular ultrathin monocrystalline Fe films

Abstract

The effects of nanostructuration on the magneto-optic properties of ultrathin monocrystalline iron films grown on MgO (001) are investigated through the magneto-optic coefficients, which have a linear and quadratic dependence on the magnetization. The photon energy dependence of such magneto-optic coefficients is determined by measuring the relative variations of the reflectivity (ΔRpp/Rpp) for p-polarized incident and reflected light (p-p polarized) when the magnetization rotates in the plane of the sample. Thick Fe films present a magneto-optical anisotropy, which has a quadratic dependence on the magnetization. Such anisotropy is strongly reduced in nanostructured iron thin films formed by nanometric iron islands. The modifications induced by the nanostructuration are stronger for the magneto-optical coefficients, which have a quadratic dependence on the magnetization in contrast to the linear terms. A self-consistent effective-medium formalism is presented that explains the modifications induced in the magneto-optical coefficients by nanostructuration.