Hysteresis-free ultra-soft magnetostrictive Zn-doped cobalt ferrite

A hysteresis-free ultra-soft ceramic magnet displaying high magnetization and a sizable mechanical response under small magnetic fields has been synthesized using a solid-state chemical reaction and thermal treatment. The material of interest is Zn-doped cobalt ferrite, which was prepared under a wide range of annealing temperatures (25 °C-1450 °C). Annealing at temperatures below 800 °C produces a large hysteresis in the magnetic response of the ceramic magnet. In contrast, high temperature annealing considerably reduces coercivity and hysteresis loss. Additionally, high-temperature annealing produces a substantial increase in magnetization, which exceeds the undoped bulk value, while quenching considerably enhances the magnetic softening of the developed ceramic, which becomes hysteresis-free. The magnetostriction manifests a Joulian behavior with a sizable magnitude of 150 ppm. The enhanced magnetic properties of the Zn-doped ceramic are attributed to microstructural changes and cationic redistribution between tetrahedral and octahedral sites within the lattice unit, which deviates from that typically known for inverted cobalt ferrite.