Study of spinel ferrites with addition of small amount of metallic elements

Spinel ferrites MPr0.1Fe1.9O4 (M=Mn, Cu, Mg) were prepared by sol-gel technique. X-ray Diffraction (XRD) showed that along with spinel phase, secondary phase (PrFeO3) appeared for all composition. Scanning electron microscopy showed the inhomogeneous grain size. Temperature dependence normalized AC susceptibility and Curie temperature of spinel ferrites revealed that in all the samples transitions from multi domain (MD) to single domain (SD) occurred. Magnetic properties exhibited the soft nature of all the samples at room temperature. Temperature dependent resistivity of all the samples increased as the temperature was enhanced, representing the semiconducting behavior. Dielectric constant and complex dielectric constants were determined at the high-frequency range of 1MHz to 3GHz. Impedance analysis clearly demonstrated the role of grains and grain boundary in the spinel ferrites. Cole-cole plots of all the samples showed only one semi-circle at high-frequency. All the samples elaborated the good picture of Koop's theory and Maxwell-Wagner model. The low value of coercivity and high magnetization of Mn-based spinel ferrites made it suitable for hyperthermia applications.