Isabelle Pasquet

About the interesting properties of mixed-valence defect spinel ferrites for mass storage media

When the spinel ferrites present a large surface/volume ratio (i.e when they are in the form of thin films or fine powders) they can be oxidized into mixed-valence defect ferrites. These original spinels have magnetic, magneto-optical and optical properties making them interesting materials for high density recording media.

Cation-Deficient Spinel Ferrites : Application for High-Density Write-Once Optical Recording

Thin films of defect spinel ferrites can be used as write-once read-many media working with blue wavelengths. In fact, because these non-stoichiometric ferrites are metastable, they can be transformed into corundum phases at moderate temperatures by a laser spot. The transformed regions have different optical indices from the starting ferrite film, making the readout process possible. Recording density of about 5 bits/µm2 was demonstrated.