Optical and magneto-optical properties of (CoFe)_x(HfO₂1)_1-X magnetic granular films

Granular films of composition (CoFe)_x(HfO₂)_1-x with continuous variation of the Co05Fe05 volume fraction in the range 0.1<;x<1 have been prepared by e-beam co-evaporation. The optical properties of the granular films have been determined from transmission and reflection spectra in the 300-1100 nm region. The optical characteristics of the films as a function of x were also determined by the ellipsometrical method at λ = 632.8 and 830 nm. The Faraday rotation in the films was determined at λ = 632.8nm. We find that the transmission and reflection spectra and the dielectric function have anomalies near the percolation threshold at x≈0.45. The spectral dispersion of Faraday effects has a peak in the region of the plasma frequency. The Faraday effect is greatly enhanced near x_p. We also find that the extraordinary Hall resistivity, measured at room temperature and at 8 kOe of applied field, increases dramatically from 0.2 to about 600 μΩ cm near the percolation threshold, These films also possess large magnetoresistance, whose values are about 4% in maximum for x = 0.35-0.45. The calculated optical and magneto-optical parameters and the extraordinary Hall resistivity, described in the framework of the effective medium approximation, are in qualitative agreement with experimental data.