A series of copper ferrite films was prepared using RF magnetron sputtering techniques. Annealing of the films at 450 and 650°C in air brought about changes of the tetragonal distortion of the spinel lattice enabling to investigate the influence of the tetragonal distortion on magnetic and magneto-optical properties. Faraday rotations up to 2°/μm at 442nm, coercive fields up to 1800Oe and high squareness of the hysteresis loops up to 0.9 could be attained by 2h annealing at 650°C followed by slow cooling.

Hexagonal Ba-ferrites of M-type (BaFe12O19) and W-type (BaMe22+Fe163+O27, Me-divalent cation) are promising materials for perpendicular magnetic recording. For this purpose it is desirable that their high uniaxial anisotropy be adjustable according to the specific requirements. Substitution of Co2+ for Fe2+/3+ cations usually decreases the magnitude of the uniaxial anisotropy and may be used to this end.In this work the influence of Co2+ content on the details of magnetic structure of Ba-hexaferrites is studied. Mossbauer spectra of Fe-57 in single crystals of BaFe12-2xCox2+Tix4+O19 and Ba(Fe2-xCox)2+Fe36O27 were measured at 293K. The dependence of the canting of magnetic moments on the concentration of Co was determined from the relative intensities of Mossbauer lines in the Zeeman nuclear multiplet and compared with the results deduced from the magnetic measurements.

Optical absorption and Faraday rotation of copper and cobalt-manganese ferrite thin films, prepared by sputtering, were measured in the visible and near infrared spectral regions. Main magneto-optical features can be explained by the respective transitions of Cu 2+ and Co 2+ ions tetrahedrally and octahedrally coordinated. Annealings at 450 and 665°C cause migration of these ions into tetrahedral positions and, consequently, increase corresponding peaks in the figure of merit Therefore, these films range among the promissing materials for the magnetooptical recording.

Recent contributions to research in magnetism and magneto-optics of hexaferrite layers, resulting from the collaboration between the above-mentioned 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 important 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 perpendicular to the film plane. Their magnetization was measured over a wide temperature range, 4.2–300 K, and in fields up to 12 T. Its dependence upon the cobalt content x in BaFe12−x−yCoxTiyO19 was also determined in the interval 0 ⩽ x ⩽ 0.8. The results were interpreted in terms of Néel theory and this, when combined with our results of Mössbauer spectra measurements, led to the formulation of a consistent model for the cation distribution in CoTi-substituted barium hexaferrites. The hysteresis-loop measurements provided data for obtaining values of anisotropy, which are in agreement with those of the bulk materials. The domain structure of thin hexaferrite layers was also studied, particularly the domain period dependence upon the sample thickness and cobalt content. The domain period dependence was found to be in very good agreement with theoretical micromagnetic calculations. Ellipsometry, reflectance photometry and Kerr/Faraday polarimetry were used to determine the optical and magneto-optical properties of hexaferrite platelets and thin layers. The complex refractive index and magneto-optic parameter were determined over the spectral range 350–850 nm and the reliability of the data was tested by comparison with photometric measurements of reflectance. The Faraday rotation 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 optical electron transitions belonging to either cobalt or iron cations occupying the tetrahedral and/or octahedral positions in the spinel block of hexagonal ferrite crystal lattice.

The measurements of the temperature dependence of electrical resistivity, Seebeck coefficient, and the saturation magnetization were performed on polycrystals Cu0.5Fe2.5O4+γWith all samples the anomalous behavior above 400°C was observed which manifested itself by a sudden increase of electrical resistivity, by the change from to type of electrical conductivity, and by the irreversible course of the magnetization. Contrary to physical properties, the chemical analysis revealed no significant changes in the composition of ferrites during the transformation. Taking into account the electrical, magnetic, and X-ray investigation it was concluded that in quenched samples (Cu1++ Fe3+) and Cu2++ Fe2+) pairs are more stable in the tetrahedral and the octahedral sites of the spinel lattice, respectively. After the transformation only Cu1+and Fe3+are present in the ferrites which initiates their decomposition into haematite and delafossite.