Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3.
Iron (III) oxide was the most common magnetic particle used in all types of magnetic storage, magnetic tapes and recording media.
Cassette tapes are made of a polyester-type plastic film with a magnetic coating.
The original magnetic material was based on gamma ferric oxide (Fe2O3).

Inexpensive cassettes commonly are labeled Low-noise, but typically are not optimized for high frequency response. For this reason,
some low-grade IEC Type I tapes have been marketed specifically as better suited for voice or AM radio programs than for music recording.
Simple voice recorders and earlier cassette decks are designed to work with standard ferric formulations. Newer tape decks usually
are built with switches and later detectors for the different BIAS and equalization requirements for higher grade tapes. The most common,
iron oxide tapes (defined by the IEC 60094 standard, as "Type I") use 120 µs equalization.
In 1973, Pfizer produced a new pigment of iron oxide, MO 2228, so a new generation of Ferric tapes has emerged, a better quality one.
The quality normally is reflected in the price; Type I cassettes generally are the cheapest. In comparative terms of sale, the Ferro cassettes occupy the first place.