Magnetocapacitance in Dy-doped Ni ferrite

Abstract

Ferromagnetic and ferroelectric characteristics of Dy substituted nickel ferrite, $\text{NiO}\ensuremath{\cdot}{\text{Fe}}_{1.925}{\text{Dy}}_{0.075}{\text{O}}_{3}$, were investigated. The material formed in the cubic inverse spinel phase with a small amount of ${\text{DyFeO}}_{3}$ as the additional phase. A small distortion of the cubic lattice was observed upon the substitution of Fe by Dy (in the $B$ site). Substitution of Dy for Fe caused a decrease in the saturation magnetization and Curie temperature of the nickel ferrite. Magnetocapacitance of $\ensuremath{-}4%$ was observed in $\text{NiO}\ensuremath{\cdot}{\text{Fe}}_{1.925}{\text{Dy}}_{0.075}{\text{O}}_{3}$ although the magnetostriction has not significantly changed with Dy substitution. The (high) dielectric constant with frequency is seen to reveal the dispersion in relaxation times.