Essential Guide to Computer Data Storage: From Floppy to DVD, The

Basics of MO Recording

All magnetic materials have a characteristic temperature, called the Curie temperature, above which they lose magnetization due to a complete disordering of their magnetic domains. At the same temperature they lose all the data they had stored before. More importantly, the material's coercivity, which is the measure of material's resistance to magnetization by the applied magnetic field (see Chapter 3), decreases as the temperature approaches the Curie point, and reaches zero when this temperature is exceeded. For the modern magnetic materials used in MO systems, this Curie temperature is on the order of 200°C. It is important (since this is a multiply erasable system) that the only change to the material when it is heated ...