Spin Fluctuations of Fe3+ Ions in Cobalt–Zinc Ferrites Using the Mössbauer Effect

Publisher Website
Google Scholar
Abstract
Resonance absorption spectra of Fe57 in CoxZn1−xFe2O4 (for x = 0.3, 0.5, and 0.75), in the temperature range from 80 to 700 °K, are discussed. The modulated lineshapes of the magnetic hyperfine spectra show features which are characteristic of relaxation effects. The theoretical line shapes, computed using the stochastic model, show good agreement with the experimental data at all temperatures for all the three compositions. For each composition, the relaxation time decreases very slowly with increase in the temperature, up to the magnetic transition temperature. Near the Néel temperature, the relaxation time starts decreasing rapidly, leading to the total collapse of the magnetic hyperfine splitting. The introduction of the Zn2+ ions in the ferrite increases the relaxation times at low temperatures (T < TN). The change is, however, negligible for the increase in the Zn2+ concentration from x = 0.5 to 0.3. This behaviour can be attributed to the role of Zn2+ ions in increasing the magnetic disorder in the ferrite. The increase in the concentration of Zn2+ ions causes the damping of the collective modes existing in an ordered ferrimagnetic system.
Keywords