Abstract
Ferrite nanoparticles of basic composition Ni0.7Mg0.3Fe2-xAlxO4 (0.0 <= x <= 0.5) were prepared through citrate gel method and characterized using XRD, TEM and dielectric spectroscopy techniques. The dielectric properties were studied as a function of frequency (42Hz-5MHz) at room temperature. The average particle size has been found between 8-17nm. The dispersion in dielectric properties and ac conductivity (sigma(ac)), with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe2+ and Fe3+ as well as between Ni2+ and Ni3+ ions at B-sites. The dielectric loss tangent (tan delta) shows abnormal behavior for the compositions 0.3, 0.4 and 0.5 which has been explained in the light of Rezlescue model.