Slashdot Mirror
"Colossal Magnetic Effect" Could Lead To Another Breakthrough In Storage Tech
Bryant writes "Scientists with the Carnegie Institution for Science have discovered what could bring yet another massive advance in memory and storage. The discovery, a magnetoresistence literally 'up to 1000 times more powerful' than the Giant Magnetoresistence Effect discovered roughly 20 years ago, which led to one of the major breakthroughs in memory, seems to be a result of high-pressure interactions between Manganites. Manganites aren't new to this game; MRAM uses Manganite layers to achieve the Magnetic Tunnel Effect needed to keep the state of memory stable. Applying significant amounts of pressure to known tech-useful materials isn't a new trick; you might recall the recent breakthrough with Europium superconductivity thanks to similar high-pressure antics."
Argonne, ILâ"Millions of people today carry around pocket-sized music players capable of holding thousands of songs, thanks to the discovery 20 years ago of a phenomenon known as the âoegiant magnetoresistance effect,â which made it possible to pack more data onto smaller and smaller hard drives. Now scientists are on the trail of another phenomenon, called the âoecolossal magnetoresistance effectâ (CMR) which is up to a thousand times more powerful and could trigger another revolution in computing technology. Understanding, and ultimately controlling, this effect and the intricate coupling between electrical conductivity and magnetism in these materials remains a challenge, however, because of competing interactions in manganites, the materials in which CMR was discovered. In the June 12, 2009, issue of the journal Physical Review Letters, a team of researchers report new progress in using high pressure techniques to unravel the subtleties of this coupling.
To study the magnetic properties of manganites, a form of manganese oxide, the research team, led by Yang Ding of the Carnegie Institutionâ(TM)s High Pressure Synergetic Center (HPSync), applied techniques called x-ray magnetic circular dichroism (XMCD) and angular-dispersive diffraction at the Advanced Photon Source (APS) of Argonne National Laboratory in Illinois. High pressure XMCD is a newly developed technique that uses high-brilliance circularly polarized x-rays to probe the magnetic state of a material under pressures of many hundreds of thousands of atmospheres inside a diamond anvil cell.
The discovery of CMR in manganite compounds has already made manganites invaluable components in technological applications. An example is magnetic tunneling junctions in soon-to-be marketed magnetic random access memory (MRAM), where the tunneling of electrical current between two thin layers of manganite material separated by an electrical insulator depends on the relative orientation of magnetization in the manganite layers. Unlike conventional RAM, MRAM could yield instant-on computers. However, no current theories can fully explain the rich physics, including CMR effects, seen in manganites.
âoeThe challenge is that there are competing interactions in manganites among the electrons that determine magnetic properties,â said Ding. âoeAnd the properties are also affected by external stimuli, such as, temperature, pressure, magnetic field, and chemical doping.â
âoePressure has a unique ability to tune the electron interactions in a clean and theoretically transparent manner,â he added. âoeIt is a direct and effective means for manipulating the behavior of electrons and could provide valuable information on the magnetic and electronic properties of manganite systems. But of all the effects, pressure effects have been the least explored.â
The researchers found that when a manganite was subjected to conditions above 230,000 times atmospheric pressure it underwent a transition in which its magnetic ordering changed from a ferromagnetic type (electron spins aligned) to an antiferromagnetic type (electron spins opposed). This transition was accompanied by a non-uniform structural distortion called the Jahn-Teller effect.
âoeIt is quite interesting to observe that uniform compression leads to a non-uniform structural change in a manganite, which was not predicted by theory,â said Ding, âoeWorking with Michel van Veenendaalâ(TM)s theoretical group at APS, we found that the predominant effect of pressure on this material is to increase the strength of an interaction known as superexchange relative to another known as the double exchange interaction. A consequence of this is that the overall ferromagnetic interactions in the system occur in a plane (two dimensions) rather than in three dimensions, which produces a non-uniform redistribution of electrons. This leads to the structural distortion.â
Another intriguing response of manganite to high p
It's a combination of persistence, random I/O and storage actually.
SSDs are good at the first two, but still have catching up to do on the latter (and price...), but as soon as a reasonably priced 1TB version comes out, that'll be a great boon...
Though I do agree that SSD's are definitely the next big thing when it comes to computer performance, there are a lot of things that need to happen before they become the definitive standard in storage. As you mention, the price/GB ratio needs to come down, but in addition to that:
- SATA 3 needs to come out. Though most SSD's don't exceed SATA 2 bus speeds, higher end SSD's like the OCZ Vertex or Intels X-25m hit 250MB/s sustained speeds. ONFi (open nand flash alliance? something like that) recently announced what is essentially the NAND 2.0 standard which doubles the speed of NAND modules, meaning next generation SSD's could easily hit sustained speeds of 500MB/s without any special tricks like internal raid. SSD's are already faster, but for better futureproof-ness and the ability to get the full potential out of SSD's, bus speeds need to increase quite a bit.
- TRIM needs to get at more OS's and SSD's support. SSD's write performance degrades with use due to a combination of the mechanics of NAND flash itself and common wear leveling algorithms. Essentially what happens is that when reading the flash blocks, all the SSD has to do is pass over and read the data. When writing though, if the block was previously written to the SSD has to erase the entire block clean and *then* write it. This is further exacerbated on MLC SSD's, where the individual transistors each store 2 bits, which on average doubles the write time with the benefit of double the space for the same price (instead of 0 or 1 like a SLC SSD, each one stores either 00, 01, 10, or 11). TRIM effectively eliminates a step from the write process on a previously used SSD by erasing blocks marked as free by the OS during an idle period, which means that write speeds degrade less over time.
- Manufacturing processes need to mature, as well as firmwares, wear-leveling algorithms, and filesystems. Unlike platter hard drives SSD's don't have decades of optimization and experience, which means higher than acceptable failure rates, extra consumer knowledge required to properly install and maintain, OS tweaks needed to fully exploit the current capabilities of SSD's, and certain technologies just not being available yet (a recent ext4 v btrfs SSD comparison on phoronix showed that btrfs was much much slower than ext4 despite the potential for btrfs to be better optimized for SSD's).
My personal belief is that by the time SSD's are halfway done with all of the above (including price/GB), they will overtake traditional HDD's in the market. The advantages of SSD's are already here and apparent, they are just expensive and a relatively young technology with a few growing pains. By the time the growing pains are half resolved SSD's will be much superior in just about every way possible, and then they will really really take off.
When I did a presentation on hard drives 3 years ago, I had already read some things saying that the Colossal Magnetorsestive Effect was the next step in read-write head technology. The Wikipedia page says the effect was discovered in 1993. This new discovery might make it more feasible, but hard drive technology developers already knew that CMR would be a part of the technology going forward.
Software sucks. Open Source sucks less.
This is not new, nor truly preliminary technology; I researched this back in 2004 and there was already a huge amount in the literature. It's just an incremental improvement and uses by and large existing thin film technologies pushed to their limit.
Most people didn't even notice the transition from regular magnetorestrictive heads to giant magnetoresistive heads, they were just incorporated naturally so that hard drive densities could further increase. This technology is the obvious and natural extension from giant magnetoresistive heads, and the increased signal to noise ratio will allow for denser drives with no doubt -- although we're already at the point where a "bit" is only made up of a few dozen magnetic domains. But in any case, this type of technology is a prerequisite for using more highly nanocrystalline magnetic materials with smaller domains...