Variation and sign change of magnetostrictive strain as a function of Ni concentration in Ni-substituted ZnFe2O4 sintered nanoparticles

Zn1-xNixFe2O4 nanoparticles were prepared with varying Ni concentration via sol-gel method. The magnetostrictive strains of sintered nanoparticles were measured using an indigenous optical cantilever beam magnetometer. The four regimes in variation of the magnetostrictive strains have been observed: (i) zero strain in the range, 0% to 25% Ni; (ii) positive (tensile) strain with a slow gradient in the range, 25% to 50% Ni; (iii) negative (compressive) strain with a fast gradient between 50% and 75% Ni; and (iv) maximum negative strain with a zero gradient between 75% and 100% Ni concentrations. The observed variation in magnetostriction is correlated with the structure of sintered nanoparticles characterized by x-ray diffraction and Mössbauer spectroscopy. The sign and magnitude of the measured magnetostrictive strain as a function of Ni concentration in the Zn1-xNixFe2O4 matrix are found to be related with the degree of inversion of the spinel structure.