Magnetic properties of Re-substituted Ni–Mn ferrite nanocrystallites

The effect of Fe3+ ions substitutions by rareearth ions on magnetic properties of nanocrystalline Ni–Mn ferrite prepared by emulsion method was investigated. X-ray diffraction pattern indicated the presence of cubic structure of spinel ferrite. The crystallite sizes increased with an increase in the heat treatment temperatures, while it decreased for the substitution of rare-earth ions. The magnetic properties were changed with types of rare-earth ions and heat treatment temperatures. Room temperature Mo¨ssbauer spectra can differentiate between superparamagnetism and ferrimagnetism in nature.