Synthesis and Magnetic Properties of Nano-sized Mn Ferrite Powder and Film

Abstract

Nano-sized manganese ferrite powders and films, <TEX>$MnFe_2O_4$</TEX>, were fabricated by the sol-gel method, and the effects of annealing temperature on the crystallographic and magnetic properties were studied by using X-ray diffractometry, field emission scanning electron microscopy, M<TEX>$\"{o}$</TEX>ssbauer spectroscopy, and vibrating sample magnetometry. X-ray diffraction spectroscopy of powder samples annealed above 523 K indicated the presence of spinel structure, and the film samples annealed above 773 K also had spinel structure. The particle size increased with the annealing temperature. For the powder samples, the Mossbauer spectra annealed above 573 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of <TEX>$Fe^{3+}$</TEX> ions. Using the M<TEX>$\"{o}$</TEX>ssbauer subspectrum area ratio the cation distribution could be written as (<TEX>$Mn_{0.52}Fe_{0.48}$</TEX>) <TEX>$[Mn_{0.48}Fe_{1.52}]$</TEX> <TEX>$O_4$</TEX>. However the spectrum annealed at 523 K only showed as a doublet due to a superparamagnetic phase. As the annealing temperature was increased, the saturation magnetization and the corecivity of the powder samples increased, as did the coercivity of film samples.