magneto-optic disk

An earlier removable, rewritable optical disk that also used magnetic technology. Introduced in 1985, magneto-optic (MO) media and drives are no longer manufactured. Refurbished drives and media are available from MaxOptix.com.

Laser-Magnetic Writing
A laser heats the optical bit to the Curie point, and a magnet changes the bit's polarity. The laser is on one side of the platter and the magnet on the other, which requires double-sided media to be manually flipped over to access the other side.

Writing initially sets the bits to zero and then writes the data in a second pass. A single-pass LIMDOW (Light Intensity Modulated Direct OverWrite) method was later added, and many drives supported the more costly LIMDOW media.

Laser Reading
A low-power laser light is reflected from the bits, and depending on their polarity, the difference in the light's rotation is sensed. See UDO, Kerr effect and optical disc.

Magneto-Optic Removable Cartridges

The 3.5" media are single sided, while the 5.25" disks are double sided. With a 50-year shelf life, up to 9.1GB of storage and capable of a million rewrites, access times are in the sub-25 ms range, much faster than optical-only CD/DVD media.