Cation distribution and magnetostrictive strain in CuFe2−xGaxO4 ceramics

Abstract

The structural, magnetic and magnetostriction properties in CuFe2-xGaxO4 ceramics synthesized by solid state reaction route and sintered at 1000 °C and 1020 °C are reported here. As per the structural analysis based on the Rietveld refinement of XRD patterns and Raman scattering, the samples crystalized into mixed spinel structures with the coexistence of tetragonal and cubic symmetry. The samples sintered at 1000 °C contained the tetragonal structure as the major structural phase, whereas the cubic phase was dominant in the samples sintered at 1020 °C. The Ga ions were found to preferentially substitute the octahedral sites. For x = 0.15 and 0.20 samples sintered at 1020 °C, a colossal grain growth was observed with grain sizes on the millimeter scale. Analysis of magnetization data in terms of fitting to law of approach to saturation revealed an enhancement of saturation magnetization due to Ga substitution. Magnetostriction strain exhibited a correlation with the occupancy of Cu2+ ions in the octahedral sites, signifying local Jahn–Teller distortion of the lattice as the mechanism behind the magnetostriction. High magnetostriction strain (−88 ppm at 5 kOe) with its rapid increase in the low-magnetic field region demonstrated the potential application of Ga-doped CuFe2O4 for magnetoelectric cofired ceramics. The colossal grain size with relatively low density of grain boundaries played an important role in the rapid rise of magnetostriction curve in low-magnetic field region.