RECORDING MEDIUM

There are two types of recording medium in general use. The first uses a thin coating of magnetic oxide and the second a thin layer of metallic magnetic film.

The magnetic oxides which are most often used are those of iron, usually gamma ferric oxide (Fe2O3) but sometimes ferrous oxide (Fe3O4) is also used. More recently chromium dioxide has been employed to achieve better packing density and greater output signals. All these oxides are produced in the form of fine acicular particles with a length-to-diameter ratio of at least ten to one. Typical lengths of these particles range from a few microns to a few tens of microns.

The process of coating magnetic tape is illustrated in Fig. 10.6. The oxide is mixed with a fluid containing ...

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