La 0.5 Sr 0.5 FeO 3 – γ Ferrite Studied by Raman Spectroscopy

Transformations of polycrystalline La 0.5 Sr 0.5 FeO 3 – γ ferrites subjected to vacuum annealing in the temperature range of 400–650°C were studied by Raman spectroscopy at ambient conditions. It was shown that the homogeneity of the sample and its local ordering depended on the vacuum annealing temperature. An increase in the vacuum annealing temperature resulted in a gradual loss of oxygen and a transition of all iron ions to the oxidation state Fe 3+ . These ferrites demonstrated a shift of the whole Raman spectra (including two-magnon modes) to higher frequencies with increasing Sr content of 0 < x < 0.5. The possible reasons for the observed effects are discussed.