Magnetic properties of Mn/Co substituted nano and bulk Ni–Zn ferrites: A comparative study

The present work shows the comparative studies on the magnetic properties of Ni0.4Zn0.6-xCoxFe2O4, (Ni–Zn–Co) and Ni0.4Zn0.6-xMnxFe2O4 (Ni–Zn–Mn) with x = 0.00 to 0.25 in steps of 0.05, ferrites synthesized by sol-gel autocombustion and conventional ceramic methods. Rietveld refinement data confirms the formation of single phase - spinel crystal structure in all the samples. The role of ferromagnetic dopants like Co and Mn on the structural, microstructural, magnetic characteristics such as Curie temperature (Tc), saturation magnetization and coercivity of NiZnFe2O4 ferrite are investigated. The influences of crystallite size obtained by using two different synthesis methods on different magnetic properties are highlighted. Continuous Tc increases have been noticed in both instances along with increasing dopant concentrations. However, compared to Ni–Zn–Mn ferrites, Ni–Zn–Co ferrites display greater Tc values. The experimental observed magnetic moments measured from vibrating sample magnetometer (VSM) are fitted with the theoretical data. The saturation magnetization values exhibit a marginal increase in the bulk form of the material as compared to its nanocrystalline counterparts. On the basis of distribution of cation and exchange interactions between magnetic cations at its tetrahedral and octahedral sublattices, the typical mechanisms accountable for the observed trends were elucidated. In addition, the dc-resistivity and dielectric loss are measured to show the application aspects of the materials in various potential device applications.