Morphology and Physical Properties of Gamma Iron Oxide

Gamma ferric oxide, γ-Fe₂O₃, is still the most widely used material for magnetic recording devices. Although there are literature references dating in the 19th century, the material was virtually unknown until systematic studies were commenced about 1925. Methods to prepare small, polycrystalline particles of various shapes, both unsupported and supported on iron metal, as well as epitaxial single-crystal films, are indicated. Data on the crystallographic and magnetic structure and other physical properties are summarized. The transformations from magnetite to gamma ferric oxide to hematite are treated. Finally, γ-Fe₂O₃ with other cation substitutions is considered. Some directions where further research is needed are suggested.