MAGNETOOPTICAL KERR ROTATION ON FE-AL2O3 ANTIGRANULOCYTES THIN-FILMS

We made measurements of polar Kerr rotation (KR) on granular thin films, composed of iron particles, with different average diameter (50 < PHI < 100 angstrom), dispersed in an amorphous Al2O3 matrix. The measurements were performed at 300 and 4 K in the wavelength interval 0.5-2.5-mu-m. The spectra observed show a decreasing tail in the visible region and then oscillations in the near infrared due to composition of the light beams reflected by the two surfaces of the sample. Values as high as 2.8-degrees of KR in the visible are obtained when a magnetic field of 4 KOe is applied perpendicular to the surface of the sample. The KR signal was also measured as a function of the temperature at the specific values of wavelength corresponding to some maxima and minima of the spectrum. The KR intensity increases as the temperature decreases down to a characteristic temperature T1*, below which it remains constant. T1* increases with increasing iron concentration and particle dimensions. This behavior is in agreement with previous results of Faraday rotation and susceptibility measurements.