Magnetic and Mössbauer Spectroscopy Studies of NiFe2O4/SiO2 Nanocomposites Synthesized by Sol-Gel Method
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Single-phase NiFe2O4 nanoparticles dispersed in SiO2 (30 wt %) matrix were synthesized by sol-gel method. The effects of the annealing temperature on the structural and magnetic properties of the samples were investigated at room temperature by X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer, and Mössbauer spectroscopy. The samples annealed at above 800∘C exhibited single-phase cubic spinel structure. The lattice constant of NiFe2O4 increased from 0.8348 to 0.8359 nm, the saturation magnetization of the samples increased from 8.24 to 29.28 emu/g, and their coercivity increased from 23.4 to 179.0 Oe when the average grain size of NiFe2O4 in the nanocomposites increased from 6 to 40 nm with varying annealing temperatures from 800 to 1200∘C. The thickness of the dead layer on the surface of the ferrite grain was obtained to about (0.76 ±0.03) nm. The study of Mössbauer spectroscopy indicated the evolution of magnetic properties of the samples from superparamagnetic to magnetically ordered character with increasing grain size of NiFe2O4.
KeywordsSol-gel method Nanocomposite Magnetic property Mössbauer spectroscopy
This work was supported by the National Natural Science Foundation of China (Nos. 21201078 and 21371071) and Foundation of Science and Technology of Jilin, China (No. 201205075).
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