MAGNETIC PROPERTIES AND STRUCTURE OF NANO-SIZE NiZn FERRITE SYNTHESIZED BY THE REFLUXING CO-PRECIPITATION METHOD

摘要

A series of nanoparticle powders of Ni_(l-x)Zn_xFe_2O_4 (x = 0, 0.3, 0.4, 0.5, 0.6 and 0.7) ferrites were synthesized by the refluxing method at relatively low temperatures. X-ray diffraction measurements were performed to yield the grain size of the particles as a function of the amount x of Zn substitution and the lattice parameter was found to increase with increasing s. M_ssbauer spectroscopy was performed at room tempera_ture. The spectra exhibit ferromagnetic hyperfine splitting sextet peaks with a doublet peak overlapped at its center as Zn contents x < 0.6. The fitted hyperfine magnetic field of the octahedral sublattice and tetrahedral sublattice all decrease with increasing Zn content. The area of the tetrahedral sublattice decreases with increasing s and that of the octahedral sites increases for low Zn concentration, as a result of substitution of iron by zinc in the tetrahedral sites. The area of the doublet increases constantly. Systematic magnetization measurements gave evidence that the doublet in the spectra originated from the superparamagnetism of the particles at room temperature as Zn content s < 0.6.