Enhancement in magnetostrictive properties of cobalt ferrite by magnetic field assisted compaction technique

Abstract

Sintered polycrystalline cobalt ferrite is a potential magnetostrictive material for torque sensor application. Significant enhancement in magnetostriction of cobalt ferrite by magnetic field assisted compaction has been reported. Nano crystalline cobalt ferrite powder was prepared by combustion synthesis method using glycine as fuel. Phase pure cobalt ferrite powder was pressed into cylindrical pellets at an applied pressure of 200 MPa using a uniaxial hydraulic press with and without magnetic field of 1 Tesla. The green pellets were sintered at 1350 °C for 12 h which resulted in sintered pellets with ∼85% of the theoretical density. The SEM micrographs of the sintered pellets revealed the microstructure to be composed of grains with average size of ∼4 μm. EBSD analysis showed that significant change in texture of cobalt ferrite has not been observed in the sample compacted in presence of magnetic field. Maximum magnetizations of 70.2 emu/g and 69.8 emu/g were observed for cobalt ferrite processed with and without magnetic field pressing, respectively. A significant enhancement in magnetostriction, (195 ppm–325 ppm) ∼65% and strain sensitivity, 35% (1.3 × 10−9 m/A to 1.8 × 10−9 m/A) have been observed for the sample pressed under magnetic field than the sample pressed without magnetic field.