Magnetic and microwave absorbing properties of Co2+ substituted nickel–zinc ferrites with the emphasis on initial permeability studies

Abstract

Nanocrystalline Co2+ substituted Zn0.35Ni0.60−xCoxFe2.05O4 (Where x=0.0, 0.1, 0.2, 0.3 and 0.4) system have been synthesized by citrate-nitrate combustion route. X-ray diffraction study shows the formation of single phase cubic spinel structure without any impurity phases. Morphological observation shows agglomerated grains with different shapes and sizes which is the typical characteristics of magnetic nanoparticles prepared by combustion route. The saturation magnetization of cobalt substituted Ni–Zn ferrites is found to be higher than that of pure Ni–Zn ferrite. The coercivity and retentivity of cobalt substituted Ni–Zn ferrite increases with the increasing cobalt content. Initial permeability and loss factor have been studied as the function of composition and frequency. The real (µ′) and imaginary (µ′′) part of initial permeability of cobalt substituted Ni–Zn ferrites decreases while its loss factor increases with the increasing cobalt content. In the lower frequency region the imaginary part of initial permeability (µ′′) of all samples is found to be decreasing rapidly with increasing frequency. The microwave absorption properties of cobalt substituted Ni–Zn ferrites were also investigated; all samples exhibit the absorption in the frequency range 2.3–2.5GHz. Thus, the prepared materials can be used as a rubber composite microwave absorber and may be useful in RADAR application.