Magnetic storage using lasers alone

Read an article today on AAAS Science Now online magazine (See Hot Idea for a Faster Hard Drive) on using lasers alone to toggle magnetic moments in specially designed ferro-magnetic materials.

The disk industry has been experimenting with bit patterned media/shingled writes (see our post on Sequential Only Disk)  and thermally or heat assisted magnetic recording (TAR or HAMR) heads for some time now.  The TAR/HAMR heads use both magnetization and heat to quickly change magnetic moments in ferro-magnetic material (see our post on When will disks become extinct).

Laser’s can magnetize!!

The new study seems to be able to do away with the magnetic recording mechanism and is able to change the magnetic value with a short focused laser burst alone.   But what does this mean for the future of disk drives.

Well one thing the article highlights is that with the new technology disks can transfer data much faster than today.   Apparently magnetic recording takes a certain interval of time (1 nanosecond) per bit and getting below that threshold was previously unattainable.

That is until this new laser magnetization came along.  According to the article they can reliably change a bits magnetic value in 1/1000th of a nanosecond with heat alone.  This may enable disk data transfers a 100X faster than available today.

Seagate’s 600GB-15Krpm 15.7 Cheetah disk has an sustained data transfer rate of from 122 to 204 MB/sec (see their 15K.7 Cheetah drive data sheet).  A 100 times that we will need a much faster interface than 16Gb/s FC which probably only transfers data at ~1600 MB/sec burst which means these drives will need like 128Gb/s FC.  In addition to the data transfer speed up, with the laser pulse alone it is much more energy efficient than the HAMR heads which need both magnetics and laser.

How soon such advances will make their way into disk drives is another question.

Is today’s 15Krpm disk speed limit due to writing speeds?

I have been struck for some time now why 3.5″ disk drives never went faster than 15Krpm.  I had always surmised it was something to do with the material mechanics at the outer diameter that limited the rotational speed.

Then when drives were shrunk to 2.5″ I thought we would see some faster rotational speed, but it never happened.  Perhaps magnetic write speeds are the problem.   At the 204MB/sec we are reading bits in under a nanosecond but write sustained data transfer is another question.  Maybe there will be a 22Krpm disk in my future?

Fixed head disks déjà vu

Ok now that that’s settled we need to work on speeding up seek times.  I  could see some sort of a rotating diffraction grating or diffraction comb taking the laser and splitting it up into multiple beams to cover each track at almost the same time, sort of like a fixed head disk of old (see IBM 2305).  This would allow disks to write seek to any track in microseconds rather than milliseconds and write data in picoseconds rather than nanoseconds.

How to do something like this for reading data off a track is yet another question.  It’s too bad we couldn’t use the laser alone to read the magnetic information as well as write it.

If you could do that and use a similar diffraction grating/comb for reading data, one could conceivably create a cost effective, competitive solution to the performance of SSD technology.  And that would be very interesting device indeed!

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