STRUCTURE AND MAGNETIC PROPERTIES OF Mn–Zn-FERRITES

Abstract

Synthesis conditions, structure and magnetic properties of Mn-Zn-ferrites prepared by spray pyrolysis of solutions of manganese, zinc and iron nitrates have been considered. The applied technique provides low-temperature (650 °C) obtaining highly dispersed (7-8 nm) powder of Mn0.5Zn0.5Fe2O4 ferrite with a narrow size distribution. Synthesis of Mn0.5Zn0.5Fe2O4 at low temperature avoids MnII → MnIII oxidation reaction that influences the ferrite properties. IR data collected from the ferrite samples obtained both in air and in N2 ambient indicate their high structural and concentration homogeneity. Magnetic measurements confirm single-phase structure of the Mn0.5Zn0.5Fe2O4 powders and give no evidence of the presence of individual iron oxide phases. Curie temperature (375-380 K) is consistent with the theoretically calculated value for Mn1-xZnxFe2O4 (x = 0.5) (Tc = 365÷385 K). Parameters of Moessbauer spectra of the ferrites are typical of FeIII state in oxide solid solutions with a considerable ionicity contribution in Fe-O bonds (δ = 0.33÷0.34 mm/s). FeII state was not revealed by Moessbauer spectroscopy that indicates the absence of FeIII → FeII reduction accompanying the MnII → MnIII oxidation process.