Bipolar magnetostriction in CoFe<inf>2</inf>O<inf>4</inf>: Effect of sintering, measurement temperature, and prestress

Magnetostrictive materials are potential candidates for many applications such as sensors, actuators, transducers, and other magnetoelectric applications. Cobalt ferrite (CoFe 2 O 4) has proven to be favorable in comparison with commonly used magnetostrictive materials due to its high magnetostriction coefficient and low cost. This work deals with the synthesis of CoFe 2 O 4 and subsequent characterization of its magnetostrictive properties. Hydrothermal route was adopted for the synthesis, and the effect of sintering and measurement temperatures on the magnetostrictive response of the synthesized samples was also established. Bipolar magnetostriction has been observed in pure CoFe 2 O 4 for the first time, and its control by means of the sintering temperature has been elucidated. The results thus reveal that the temperature is an important parameter in determining the magnetostrictive characteristics of CoFe 2 O 4. The switching from bipolar to unipolar magnetostriction under elevated sintering and measurement temperatures was also observed, and this was owed to the crystal anisotropy of the material. The effect of prestress on the magnetostriction was also studied, wherein it was observed that the application of a compressive prestress resulted in broadening of the magnetostriction loops. The reported bipolar magnetostrictive characteristics are quite interesting and hence can prove to be cost-effective in comparison with existing magnetostrictive materials.