The magnetic Fe-Ti oxides of basaltic rocks of different ages from Central Slovakia, Bohemian Massif, Syria and Nigeria have been studied by electron-microprobe analysis, X-ray powder diffraction, Mössbauer spectroscopy, and by fully automated measurements of the change of magnetic susceptibility (κ) of the samples in the range -196 to 620 °C. The compositions of dominant magnetic phases, also oxidation parameter z of Fe-Ti oxides of basaltic rocks under study have been evaluated and derived, comparing our laboratory data with those published by other authors. A following compositions and oxidation parameters z of Fe-Ti oxides of four selected groups of basaltic rocks are supposed to be actual:
— Fe_2.3Ti_0.7O₄–Fe_2.4Ti_0.6O₄ (z ≈ 0.15–0.35)
— Fe_2.28Ti_0.72O₄–Fe_2.62Ti_0.38 O_{4<'sub> (z ≈ 0.12–0.32)
— Fe2.95Ti0.05O4–Fe3O4 (+ Fe2O3)
A solution of the nature of Fe-Ti oxides is supposed to be very problematic. In true multi-domain particles of the samples k should be approximately constant over a rather extended temperature interval. Many authors have concluded that the properties of all compositions are consistent with multi-domain structure. Surprisingly, titanomagnetites with low Curie temperatures exhibit a variation of κ with temperature. These titanomagnetites have shown a characteristic cusps behaviour, which is typical for spin-glasses. It means that actual temperature dependence of κ for coarse-grained high-titanium titanomagnetites is quite different from that, expected for large multi-domain grains.}