Effect of α-Fe2O3 phase on structural, magnetic and dielectric properties of Mn–Zn ferrite nanoparticles Original Research Article

Structural, magnetic and dielectric properties of Mn–Zn ferrites (with nominal composition MnxZn1−xFe2O4−δ) prepared by two methods (evaporation and auto-combustion) and annealed at temperatures up to Ta=900 °C are compared. Rietveld analysis of the X-ray diffraction (XRD) patterns shows the presence of the cubic ferrite phase and hematite, the concentration of latter decreasing with increase in the annealing temperature. For samples annealed at 900 °C, x=0.26 (x=−0.36) is determined for the sample prepared by evaporation (auto-combustion) technique. Morphology and crystallite size (t) were determined by SEM and TEM respectively. Magnetic measurements at room temperature showed improvements in the saturation magnetization with increase in annealing temperature; this effect is related to the increase in crystallite size (t) with increase in Ta. Similar improvements in the dielectric constants and dielectric loss (measured in the frequency range of 100 kHz to 5 HMz) are observed with increase in Ta. It is inferred that annealing at even higher Ta is needed to achieve better magnetic and dielectric properties.