Structural, magnetic and Mössbauer spectral studies of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite powders

Nanocrystalline Ni0.5Zn0.5Fe2O4 powders, synthesized by a combustion method are investigated by X-ray diffraction, vibrating sample magnetometry and Mössbauer spectroscopic techniques. We adopt a strategy to systematically control the particle sizes between 4 and 45 nm simply by changing the elemental stoichiometric coefficient, Φe, of the combustion mixture. Curie temperature of the superparamagnetic particles of size 4 nm is higher than that of the bulk particles. Interestingly, bigger particles (45 nm) show a comparable room temperature saturation magnetization and exceptionally very high Curie temperature of 833 K, when compared to that of the bulk Ni0.5Zn0.5Fe2O4 material (563 K).

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► Control of sizes (4–45 nm) by changing elemental stoichiometric coefficient, Φe.
► Particles obtained from Φe > 1 show increase in Curie temperature, TC, by 82 K.
► Exceptionally high TC of 833 K for particles obtained from stoichiometric mixture.
► Off-stoichiometric spinel phase formation with frustrated surface spins is explored.
► Structural and magnetic properties are a complex function of processing parameters.