Specific features of infrared absorption in films materials subjected to a magnetic field

The reflection spectra and magnetorefractive effect (MRE) of metal (Co, CoFe), semiconductor (Si, GaAs), and granular and amorphous Co₃₀Ag₇₀ and Co₅₉Fe₅Ni₁₀Si₁₁B₁₅ films are studied in the IR spectral region at λ=2.5–25 μm. It is found that the IR optical properties of the ferromagnetic metal films can be described with regard to light absorption due to electron transitions in the two spin systems. The MRE is found to occur in both the ferromagnetic (Co, CoFe) and semiconductor (Si, GaAs) films. The amplitude and shape of the MRE are determined for the p and s polarizations of light. It is shown that, to a first approximation, the IR optical properties of the films with giant magnetoresistance can be described by the Drude theory, while the MRE is explained on the basis of a modified Hagen-Rubens relation. Variations in the IR reflection of semiconductor or amorphous metal films in the magnetic field are found to depend on the degree of polarization of localized electron states at the Fermi level.