magneto-optical disk

magneto-optical disk

(hardware, storage)
(MO) A plastic or glass disk coated with a compound (often TbFeCo) with special optical, magnetic and thermal properties. The disk is read by bouncing a low-intensity laser off the disk. Originally the laser was infrared, but frequencies up to blue may be possible giving higher storage density. The polarisation of the reflected light depends on the polarity of the stored magnetic field.

To write, a higher intensity laser heats the coating up to its Curie point, allowing its magnetisation to be altered in a way that is retained when it has cooled.

Although optical, they appear as hard drives to the operating system and do not require a special filesystem (they can be formatted as FAT, HPFS, NTFS, etc.).

The initial 5.25" MO drives, introduced at the end of the 1980s, were the size of a full-height 5.25" hard drive (like in IBM PC XT) and the disks looked like a CD-ROM enclosed in an old-style cartridge

In 2006, a 3.5" drive has the size of 1.44 megabyte diskette drive with disks about the size of a regular 1.44MB floppy disc but twice the thickness.

Storage FAQ.
This article is provided by FOLDOC - Free Online Dictionary of Computing (
References in periodicals archive ?
A magneto-optical disk containing personal information on 224,183 subscribers has been lost by Japanese mobile operator KDDI.
In hardware terms, level one data is kept on the network server, level two data is migrated to a storage device such as a magneto-optical disk (MO) jukebox, and level three data is archived in a tape storage library or removed and stored in a vault.
With a rewriteable magneto-optical disk, data can be recorded on the disk, erased and then replaced with new data; such disks cost about $150 each.
Wal-Mart's system, dubbed Computer-Based Learning (CBL), has one to five computer terminals in each store, with CD-ROM and magneto-optical disk drives.
Canon's CFView and CF Index PC software coupled with Canon's Diskfile Drive 5001S, a magneto-optical disk drive, make a desktop PC into a Canofile workstation to index and view documents on a Canofile disk.
* NEW BACKUP techniques also are available: minicassette and digital audio tape systems, Bernoulli drives, mirroring and magneto-optical disk drives.
The growing demand for high-density storage in the multimedia era has been met by TDK Electronics with its new MO-R128 rewritable magneto-optical disk, a 3.5-inch, high-capacity (128 MB) disk.
The LF-7010 rewritable optical disk drive differs from magneto-optical disk drives in that it uses a recently improved phase-change technology to overwrite information in one pass directly onto a rewritable optical disk.
The program recognises any HFS/HFS+/UFS volume including hard disks, magneto-optical disks, SyQuest cartridges, Zip cartridges, iDisks, and AppleShare, samba and NFS servers.
"The magneto-optical disks hold roughly 5 GB instead of only 700 MB like a CD, so we have fewer disks and the ability to rewrite," says Black.

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