Talk:Magneto-optical drive

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Experience with MO DrivesEdit

I work for a large corporation that has used MO drives for the last 9+ years, starting with 2.6 gb drives and now with 9.1 GB 5.25" drives which are backwards compatible (can read 2.6 GB disks). The newest media we use is made by Verbatim and has a "life expectancy > 40 years". We currently have the drives under a maintenance contract from Kodak Eastman. I came to the site looking for information about media failure rates because we are starting to have a significant number of media (and drives for that matter) fail.--Mrmystery44 (talk) 19:04, 5 February 2008 (UTC)


The description in the "recent progress" section is terrible. It expands when read? How is that possible? Perhaps someone should flag this for rewrite.

But that's not why I came here. I was curious about the life expectancy of MO media, and this gives no hint. Anyone know? -- anon user (27 Oct 2005)

Can anyone provide information on CD-MO (Magneto-optical rewritable CDs that came much before phase-change CD-RW)? They were introduced as long as in 1988, but there hardly seem to be any references to them on the net, other than theoretical descriptions. E.g. what kind recorders can write them and are disks/devices still made? Can they be read in normal CD-Drives? At what speeds could they be written? Why don't they seem to be used a lot (if at all) nowadays? EpiVictor 13:55, 12 January 2006 (UTC)

The CD-MO format was never commercialized. It differs from all other CD formats by having MO technology implemented on Compact Disc format media, which makes it incompatible with 'regular' CDs (among other things, MO uses concentric tracks as opposed to the single spiral track used on [non-CD-MO] CDs). There was simply no point in this hybridisation. Those who embrace MO technology (mostly businesses in the early days) would prefer the protection and convenience that cartridges offer. —Broccoli 00:35, 11 May 2006 (UTC)
Thanks to User:EpiVictor, who questioned my dubious claim above about CD-MO format, I have partially amended my comment. —Broccoli 05:52, 5 January 2007 (UTC)

I've added an image of a 230MB MO disk, which does leave the page somewhat overburdened with images. I'm just the photographer, perhaps someone with a bit more article-nous can decide which images work the best - delete at will. danamania 16:12, 20 March 2006 (UTC)

Reversion to 15:00, 13 September 2006Edit

I am reverting this page to 15:00, 13 September 2006 because a large part of the article was blanked, and in the next edit the page was vandalized. Ogredrew 10:22, 26 September 2006 (UTC)

Fujitsu no longer a vendorEdit

According to <>, they have ceased selling drives at least in Europe. Their global page is inconsistent, but all drives are actually marked as obsolete products. So it seems they no longer make or sell drives.

This development might be relevant for the "Recent progress" section, as Fujitsu was afaik the only remaining vendor of 3.5" drives. —The preceding unsigned comment was added by (talk) 09:02, 22 February 2007 (UTC).

As I remember, the material used in the MO is rather ferrimagnetic but not ferromagnetic. The laser applied on the material does not heat the material up to Curie temperature but to the so-called compensation temperature, where two magnetic components compensate each other.

You remember wrong. The laser definitely heats the material to its Curie temperature. (talk) 09:27, 12 November 2011 (UTC)

Table with sizes and capacities?Edit

90mm had only 250 and 640MB? Larger sizes 1.2Gb, 3.??, ??? --Flightsoffancy (talk) 19:25, 31 January 2010 (UTC)

I found the following in a 'Read Me' file on a 128MB 90mm MO Disk:
Reorder Numbers:
3M Macintosh Formatted 128 MB:    44266
3M Macintosh Formatted 230 MB:    44441
3M Macintosh Formatted 590 MB:    15250
3M Macintosh Formatted 650 MB:    15251
3M Macintosh Formatted   1.2 GB:    44442
3M Macintosh Formatted   1.3 GB:    44443

Ziltro (talk) 20:35, 7 April 2011 (UTC)

Technical aspectsEdit

Clarified the description of erase/write cycle on older version of MO. [1] --ElectroWolf (talk) 09:14, 26 January 2011 (UTC)


How exactly is the optical kerr effect used?Edit

If I understand correctly a ferromagnetic layer is written to by first heating (by laser light) then cooling down with desired magnetic orientation; then it can be read by shining light with known polarization state, which upon passing throught the magnetooptic kerr effect layer will have changed its polarization state depending on the magnetic field (of the ferromagnetic layer). When I look up magnetooptic and electrooptic effects the most sensitive materials require quite long optical paths through the medium with strong magnetic or electric fields to be measurable... how can an extremely thin layer of magnetooptic kerr effect material produce a measurable change? Are there any numbers available of field strength, exact magnetooptic layer material used,...?

Is it possible to look at say a minidisc surface through a polarization beam splitter and watch the effect of a strong magnet closeby? — Preceding unsigned comment added by (talk) 21:38, 7 November 2011 (UTC)

As I understand it, the change in polarisation is of the order of plus or minus half a degree over the thickness of the active layer (bearing in mind that the light from the laser passes through the layer twice). This is enough of a change for the detector to detect whether the change is plus or minus as that is all it has to do. (talk) 14:41, 8 November 2011 (UTC)
Sure a change of half a degree can be detected, but that is still a HUGE magneto optic kerr effect for the thin layer, I can find no material with that kind of magnetooptic kerr effect..., I suspect a trick is used but its not clear which (if the magneto optic kerr effect is not simply a lie to confuse the competition...) — Preceding unsigned comment added by (talk) 21:39, 8 November 2011 (UTC)
I am merely quoting Sony who manufacture the Magneto Optical Mini Disc. Please sign your comments by adding 4 tildes (~~~~) at the end. (talk) 09:28, 12 November 2011 (UTC)

Bad ChronologyEdit

I don't have the right information or references for it, but this article has nonsense for history. It says MOs came out in 1985. Then it says that NeXt was the first vendor to sell MOs. NeXt didn't even sell computers until 1989-1990! Can someone with correct information please fix this?-- (talk) 06:28, 6 March 2012 (UTC)

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