Studies on the magnetic, magnetostrictive and electrical properties of sol–gel synthesized Zn doped nickel ferrite

Zinc doped nickel ferrite i.e., Ni1−xZnxFe2O4 (0 ≤ x ≤ 0.6) have been prepared by using sol–gel method. X-ray diffraction of these samples shows the presence of single-phase cubic spinel structure. The room temperature magnetic measurements showed that saturation magnetization (Ms) increases with the substitution of Zn2+ ions up to x = 0.4 and thereafter it begins to decrease, whereas magnetostriction (λ) value decreases with the addition of Zn2+ in the Ni–Zn ferrite. Dielectric permittivity (ɛ′), dielectric loss tangent (tan δ) and AC conductivity (σAC) for all the prepared samples have been studied as a function of frequency and composition in the range from 0.05 Hz to 10 MHz at room temperature. It has been observed that initially ɛ′, tan δ and σAC decreases with the substitution of Zn2+ up to x = 0.4 and then increases with the further addition of Zn2+ ions. Variation in the slope parameter s with zinc contents indicates the presence of different type of conduction mechanism in different compositions. The dielectric loss curves exhibit relaxation peaks which shift with the addition of Zn contents. The results have been explained on the basis of space charge polarization according to Maxwell–Wagner's two-layer model and the hopping of charges between Fe2+ and Fe3+ as well as between Ni3+ and Ni2+ ions at the octahedral sites.

Research highlights
► The effect of Zn contents on the magnetic, magnetostrictive and electrical properties of the nickel ferrite has been studied.
► The saturation magnetization increases with Zn contents up to x = 0.4 and thereafter it begins to decrease.
► The slope of magnetostriction decreases with the addition of Zn contents except for x = 0.4 where it is found to be larger in all Zn doped samples.
► Dielectric permittivity, ac conductivity and dielectric loss decreases with increasing Zn content up to x = 0.4 and then increases with further addition of Zn.
► The results show that composition x = 0.4 is the most suitable constituent phase for magnetoelectric (ME) composites due to its high values of magnetization and strain derivative while dielectric constant and electrical conductivity shows low trend.