
The main component of natural magnets: iron tetroxide, chemical formula Fe3O4, often called "magnetic iron oxide". It is a magnetic black crystal. It can be regarded as a compound composed of ferrous oxide and iron oxide. It is insoluble in water and cannot react with water. Reacts with acid, insoluble in alkali.
Mainly used for making primers and topcoats, magnetic materials for the electronics industry, and rust inhibitors for the construction industry. Limited by Joule magnetostriction, conventional magnets can only be used as actuators that apply force in one direction. Even actuation in only two directions requires a large number of bulky magnets, which increases build-up and reduces efficiency. Instead, non-Joule magnetostrictive magnets can be retracted in all directions simultaneously, so making compact omnidirectional actuators would be easy to implement.