Crystal Structure of Ferrites

Abstract

In Chapter 1, we built up a series of magnetic structures of increasing complexity starting with the electron, progressing to the atom (or ion) and finally, focusing on the domain. Although the domain is important in explaining cooperative magnetic phenomena, the next larger physical magnetic entity after the ion is the ferrite unit cell or the crystal structure. The crystal structure of a ferrite can be regarded as an interlocking network of positively-charged metal ions (Fe⁺⁺⁺ M²⁺) and negatively-charged divalent oxygen ions (C⁼). Hereafter in the sections on ferrites, we will be dealing with ions rather than atoms and specifically in magnetic oxide ceramics. Since the crystal contains a network of ionic bonds, we can think of the crystal as a giant molecule. The arrangement of the ions or the crystal structure of the ferrite will play a most important role in determining the magnetic interactions and therefore, the magnetic properties.