The structure and magnetic properties of Zn1-xNixFe2O4 ferrite nanoparticles prepared by sol-gel auto-combustion

• Published in: Journal of magnetism and magnetic materials 2007-05, Vol.312 (1), p.126-130
• Main Authors: ZHANG, H. E, ZHANG, B. F, WANG, G. F, DONG, X. H, GAO, Y
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Magnetic properties and materials; Magnetic properties of nanostructures; Materials science; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Physics
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2006.09.016

Zn1-xNixFe2O4 ferrite nanoparticles were prepared by sol-gel auto-combustion and then annealed at 700 deg C for 4h. The results of differential thermal analysis indicate that the thermal decomposition temperature is about 210 deg C and Ni-Zn ferrite nanoparticles could be synthesized in the self-propagating combustion process. The microstructure and magnetic properties were investigated by means of X-ray diffraction, scanning electron microscope, and Vibrating sample magnetometer. It is observed that all the spherical nanoparticles with an average grain size of about 35nm are of pure spinel cubic structure. The crystal lattice constant declines gradually with increasing x from 0.8435nm (x=0.20) to 0.8352nm (x=1.00). Different from the composition of Zn0.5Ni0.5Fe2O4 for the bulk, the maximum Ms is found in the composition of Zn0.3Ni0.7Fe2O4 for nanoparticles. The Hc of samples is much larger than the bulk ferrites and increases with the enlarging x. The results of Zn0.3Ni0.7Fe2O4 annealed at different temperatures indicate that the maximum Ms (83.2emu/g) appears in the sample annealed at 900 deg C. The Hc of Zn0.3Ni0.7Fe2O4 firstly increases slightly as the grain size increases, and presents a maximum value of 115Oe when the grains grow up to about 30nm, and then declines rapidly with the grains further growing. The critical diameter (under the critical diameter, the grain is of single domain) of Zn0.3Ni0.7Fe2O4 nanoparticles is found to be about 30nm.