Optical and magneto-optical properties of (CoFe)(x)(HfO(2)1)(1-x) magneticgranular films

Granular films of composition (CoFe)(x)(HfO2)(1-x) with continuous variatio n of the Co0.5Fe0.5 volume fraction in the range 0.1 < x < 1 have been prep ared by e-beam co-evaporation. The optical properties of the granular films have been determined from transmission and reflection spectra in the 300-1 100 nm region. The optical characteristics of the films as a function of x were also determined by the ellipsometrical method at lambda = 632.8 and 83 0 nm. The Faraday rotation in the films was determined at lambda = 632.8 nm . We find that the transmission and reflection spectra and the dielectric f unction have anomalies near the percolation threshold at x approximate to 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 temper ature and at 8 kOe of applied field, increases dramatically from 0.2 to abo ut 600 mu Omega 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 extrao rdinary Hall resistivity, described in the framework of the effective mediu m approximation, are in qualitative agreement with experimental data. (C) 2 000 American Institute of Physics. [S0021-8979(00)02604-9].