Sonochemical Synthesis and Characterization of Manganese Ferrite Nanoparticles

This paper reports sonochemical synthesis and characterization of Mn-ferrite nanoparticles using acetates precursors. Mn-ferrite synthesis requires external calcination of oxide precursors formed by sonication. pH does not play a dominant role in the synthesis. Collisions between metal oxide particles induced by shock waves generated by transient cavitation are unable to cross the activation energy barrier for the formation of ferrite. The calcination temperature is a significant parameter that influences the magnetic properties of ferrites. The size, coercivity, and saturation magnetization of ferrite particles increases with the calcination temperature. Ferrites formed at calcination temperatures of 650, 750, and 850 degrees C show ferromagnetic behavior with easy axis magnetization. Calcination at 950 degrees C leads to the formation of rods with grain growth that introduces large shape anisotropy. The magnetization curve for rods does not reach saturation, indicating paramagnetic behavior. The cause leading to this, effect is nonalignment of the easy axis of magnetization with the direction of the applied magnetic field, resulting in hard axis magnetization.