MAGNETISM AND MAGNETOOPTICS OF HEXAFERRITE LAYERS

Recent contributions to research in magnetism and magneto-optics of he xaferrite layers, resulting from the collaboration between the above-m entioned institutions, are comprehensively reviewed. The pulsed laser deposition (PLD) technique is described and its main features, relying on the plume diagnostics and correct oxygen pressure, both being impo rtant for the deposition of hexaferrites of complex stoichiometry, are highlighted. The fabricated layers were investigated structurally and it was found that they are highly textured with the c-axis perpendicu lar to the film plane. Their magnetization was measured over a wide te mperature range, 4.2-300 K, and in fields up to 12 T. Its dependence u pon the cobalt content x in BaFe12-x-yCoxTiyO19 was also determined in the interval 0 less than or equal to x less than or equal to 0.8. The results were interpreted in terms of Neel theory and this, when combi ned with our results of Mossbauer spectra measurements, led to the for mulation of a consistent model for the cation distribution in Co-Ti-su bstituted barium hexaferrites. The hysteresis-loop measurements provid ed data for obtaining values of anisotropy, which are in agreement wit h those of the bulk materials. The domain structure of thin hexaferrit e layers was also studied, particularly the domain period dependence u pon the sample thickness and cobalt content. The domain period depende nce was found to be in very good agreement with theoretical micromagne tic calculations. Ellipsometry, reflectance photometry and Kerr/Farada y polarimetry were used to determine the optical and magneto-optical p roperties of hexaferrite platelets and thin layers. The complex refrac tive index and magneto-optic parameter were determined over the spectr al range 350-850 nm and the reliability of the data was tested by comp arison with photometric measurements of reflectance. The Faraday rotat ion and absorption spectra of substituted hexaferrite thin layers were measured in the 500-2000 nm wavelength range at room temperature and 80 K. The results obtained are interpreted in terms of single-ion opti cal electron transitions belonging to either cobalt or iron cations oc cupying the tetrahedral and/or octahedral positions in the spinel bloc k of hexagonal ferrite crystal lattice.