Ferrimagnetic materials commonly known as ferrites, can be generally represented by chemical formula XOFe₂O₃,

where X stands for Mn, Co, Ni, Cu, Mg, Zn, Cd etc.

If X is Fe, then compound is Fe₃O₄.

X-ray crystallography proves that ferrites are usually crystals and have a spine structure.

Reference: This article is referred from my book “electrical engineering materials” having ISBN 978-81-272-5069-0. In case of any doubt, comment it or post it.