Effect of Sr-substitution on the structural and magnetoelectric properties of Ni-Zn ferrites

Abstract

Spinel type polycrystalline Ni_0.6-xZn_0.4Sr_xFe₂O₄ (x = 0.0, 0.05, 0.10, 0.15 and 0.20) ferrites are synthesized by solid state reaction method. X-ray diffraction (XRD) pattern reveals the formation of spinel structure with two secondary phases Sr₂FeO₄ and SrFe₁₂O₁₉ for higher concentration of Sr (0.15 and 0.20). An increase in lattice constant is observed with the increase of Sr content in the lattice. The density of the samples is found to decrease whereas porosity increases with the substitution of Sr²⁺ ions. Microstructural investigation shows that the grain size increases with the increase of Sr content. Magnetic hysteresis is investigated at room temperature. All the samples exhibit lower coercivity values indicating that the materials belong to the class of soft ferrites. The saturation magnetization is found to decrease with Sr content which is attributed to Néel’s two sub-lattice model of ferrites. The real permeability of the samples remains almost constant up to a certain frequency and then falls rapidly. Improved dielectric constant is observed in the Sr²⁺ substituted samples. The electrical conduction in these ferrites is explained on the basis of hopping mechanism between the Fe²⁺ and Fe³⁺ ions.

Bangladesh Journal of Physics, 26(2), 1-20, December 2019