Spintronics - new physics just keeps pouring out

Innovation, eh? Does it really mean just another smartphone with a slightly whizzier interface?
Written by Rupert Goodwins, Contributor

Innovation, eh? Does it really mean just another smartphone with a slightly whizzier interface? Yet another x86 processor that makes servers go a bit faster? A search engine that throws up restful pictures of pretty landscapes?

I say no. Round these parts, innovation means high-brilliance circularly polarized x-rays probing the magnetic state of a material under pressures of many hundreds of thousands of atmospheres inside a diamond anvil cell. That's what's being reported by a research team led by Yang Ding of the Carnegie Institution’s High Pressure Synergetic Center (HPSync), where the technique - called x-ray magnetic circular dichroism (XMCD, no, not the comic) - has revealed the Colossal Magnetoresistance Effect.

Savour that efflorescence of Trekkie technobabble, because it's a signpost to new worlds. You may have heard of the GIant Magnetoresistance Effect, which was discovered twenty years ago and is now one key technology in the hard disks we have that are small and cheap enough to fit into iPods and capacious enough to hold years of music. GME is a piece of material science that couples tiny changes in magnetism to easily detectable changes in resistance, leading to extremely high data densities on hard disk platters. CME is like that, only thousands of times more sensitive.

As you may be able to guess, though, it's a long way from being pocket and wallet compatible. What Ding and co are taking advantage of is that when you compress mangantites - a form of manganese oxide - under incredible stresses and flood them with incredibly high energy X-rays, you can gain exquisite control over the magnetic state of the material. Such control is at the heart of spintronics, which is one of the best candidates to take over from bog-standard silicon tech when that runs out of steam.

This doesn't mean, however, that we'll have to carry around super-energetic X-ray sources in 100,000 atmosphere pressure cells in the next generation iPhone (although the idea does have its attractions). This experimental set-up is more a window into a whole new physics, much of which is unexplained, that will also exist in more mundane places. Once we've got a theoretical hook into it, there'll be plenty more to play with that doesn't need XMCD.

This isn't by any means the only new research pulling in exciting new directions - perhaps the most thrilling part of solid state physics research is that there's so much of it, with new basic effects and peculiarities being reported almost weekly. There's so much it's impossible to keep up: quite a different dynamic to earlier flaps like high temperature superconductors and (ahem) cold fusion, where initially exciting reports congealed into one or two strands of research that haven't fulfilled the first hype.

Now, the real revolution is in the raw techniques for investigation, many built on the back of the practical work coming out of the silicon industry, and the sheer amount of computational power available to quotidian research.

We don't know what we'll find, but we do know there's an awful lot of it to uncover. Exciting? We don't know the half of it.

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