Relation between superparamagnetic relaxation and optical properties

We study the influence of the transition between ferromagnetism and superparamagnetism on optical properties. The samples are thin nanocermet films where ferromagnetic monodomain inclusions of Ni are embedded in an AlN matrix. The optical measurements, performed on a Fourier transform spectrometer in the far infrared range, are compared with calculations of the dielectric function and the magnetic permeability using a model of the effective medium.