Colossal resistivity with diminished tangent loss in Zn–Ni ferrite nanoparticles

We have investigated the electrical and magnetic response of the sol–gel synthesized Zn x Ni 1− x Fe 2 O 4 ( x = 0.0, 0.5 and 1) nanoparticles. The ratio of A-site sextet intensity to that of B-site sextet is featured in terms of divergence in coordination of Fe 3+ ions from four-fold (A-site) to six-fold (B-site). Canted spin structure and weakening of Fe 3+ (A)–Fe 3+ (B) interactions at the surface of the nanoparticles assign the reduced value of room temperature magnetization in these nanoparticles. Shift of the blocking temperature with Zn content is ascribed to the change in the magnetic anisotropy. Colossal resistivity and reduced dielectric constant are discussed on the basis of dangling bond, superparamagnetic character, canted spin structure and polarizability of the cations. Diminished tangent loss is stipulated in terms of decrease in magnetocrystalline anisotropy and collapse of long-range magnetic order. We report colossal resistivity (i.e. 3.15 × 10 9 Ω cm), reduced dielectric constant (3.97) and diminished tangent loss (0.07) for Ni 0.5 Zn 0.5 Fe 2 O 4 nanoparticles.