Role of Cr3+ ions on the microstructure development, and magnetic phase evolution of Ni0.7Zn0.3Fe2O4 ferrite nanoparticles

A series of ferrite samples with the chemical formula Ni(0.7)Zn(0.3)CrxFe(2-x)O(4) (x = 0.0-0.5) were prepared by a sol-gel auto-combustion method and annealed at 600 degrees C for 4 h. The resultant powders were investigated by various techniques, including X-ray diffractometry (XRD), vibrating sample magnetometry (VSM), and permeability studies. The prepared samples have a cubic spinel structure with no impurity phase. As the Cr3+ content x increases, bulk density and crystallite size decrease, whereas porosity increases. The saturation magnetization decreases linearly from 58.31 to 42.90 emu/g with increasing Cr3+ content. However, coercivity increases with increasing Cr3+ substitution. The magnetic moments calculated from Neel's molecular-field model are in agreement in the experiment results. The initial permeability (mu(i)) decreases with increasing Cr3+ substitution. The decrease in initial permeability (mu(i)) is attributed to decrease in magnetization on addition of Cr3+. The real part of the permeability decreases gradually with increasing frequency in accordance with Snoek's law. The Curie temperature decreases linearly with increasing Cr3+ content. (C) 2011 Elsevier B.V. All rights reserved.