Ferrimagnetism
Ferrimagnetism occurs in an oxide of iron called magnetite, with chemical formula Fe3O4. The mineral is historically significant because, millenia ago, humans discovered that natural magnetite lodestone always pointed north when floated in water, making the first navigational compass. The magnetism is a result of the alignment of tiny regions in the material called “magnetic domains” in the material. For ferrimagnetism, neighboring magnetic domains lie in opposite directions. Normally, the opposite ordering cancels out the overall magnetic field of an object; however, in a ferrimagnet, small differences between neighboring domains makes a magnetic field possible.
Ferromagnetism:
Ferromagnetism occurs in some elements such as iron, nickel and cobalt. In these elements, the magnetic domains align in the same direction and parallel to each other to produce strong permanent magnets. Recently, rare earth elements such as neodymium have been found to greatly intensify ferromagnetism, resulting in powerful, compact permanent magnets.
