Co substituted Ni–Zn ferrites with tunable dielectric and magnetic response for high-frequency applications

Abstract

Microwave ferrites are the most promising materials for high frequency and high-power devices. In this work, Co substituted Ni–Zn ferrites (Ni0.5-xZn0.5CoxFe2O4; x = 0–0.4) are synthesized, and the structural, morphology, dielectric, magnetic response are systematically investigated. The X-ray diffraction pattern (XRD) pattern confirmed the formation of pristine cubic phase alone without any secondary phase in all the samples. Substitution of Co2+ resulted in increased crystallite size and lattice constant. Raman peak intensity is suppressed, and a shift towards a lower wavenumber is observed with Co substitution. The change in position and intensity is analyzed and attributed to the change in cationic distribution in tetrahedral and octahedral positions by deconvoluting the Raman peaks. The Energy-dispersive X-ray spectroscopy (EDAX) analysis confirms the stoichiometry of compounds. The real permittivity and tan δ are decreased with the dilution of Co (x = 0: ε' = 24, tan δ = 0.015; x = 0.4: ε' = 11, tan δ = 0.035 @ 1 MHz). Further, permeability initially increased in the X band frequency range and decreased with increasing Co concentration. An increase in the saturation magnetization was observed initially with increased Co content and a decrease after x = 0.2. A maximum saturation magnetization (Ms = 63.3 emu/g) observed for x = 0.2 composition. Interestingly, a giant coercivity and high effective magnetocrystalline anisotropy are observed with the incorporation of Co at low temperatures (5 K). The low dielectric loss, high saturation magnetization, and low coercivity at room temperature of Co substituted Ni–Zn ferrites suggest that these compounds are potential candidates for high-frequency devices (circulators).