Ultra-fast magnetic reversal observed

Apr 13, 2011
Ultra-fast magnetic reversal observed

A newly discovered magnetic phenomenon could accelerate data storage by several orders of magnitude.

With a constantly growing flood of information, we are being inundated with increasing quantities of data, which we in turn want to process faster than ever. Oddly, the physical limit to the recording speed of storage media has remained largely unresearched. In experiments performed on the BESSY II of Helmholtz-Zentrum Berlin, Dutch researchers have now achieved ultrafast magnetic reversal and discovered a surprising phenomenon.

In magnetic memory, data is encoded by reversing the magnetization of tiny points. Such memory works using the so-called magnetic moments of atoms, which can be in either "parallel" or "antiparallel" alignment in the storage medium to represent to "0" and "1".

The alignment is determined by a quantum mechanical effect called "exchange interaction". This is the strongest and therefore the fastest "force" in magnetism. It takes less than a hundred femtoseconds to restore magnetic order if it has been disturbed. One femtosecond is a millionth of a billionth of a second. Ilie Radu and his colleagues have now studied the hitherto unknown behaviour of magnetic alignment before the exchange interaction kicks in. Together with researchers from Berlin and York, they have published their results in Nature.

For their experiment, the researchers needed an ultra-short laser pulse to heat the material and thus induce magnetic reversal. They also needed an equally short X-ray pulse to observe how the magnetization changed. This unique combination of a and circular polarized, femtosecond X-ray light is available in one place in the world: at the synchrotron radiation source BESSY II in Berlin, Germany.

In their experiment, the scientists studied an alloy of gadolinium, iron and cobalt (GdFeCo), in which the magnetic moments naturally align antiparallel. They fired a laser pulse lasting 60 femtoseconds at the GdFeCo and observed the reversal using the circular-polarized X-ray light, which also allowed them to distinguish the individual elements. What they observed came as a complete surprise: The Fe atoms already reversed their magnetization after 300 femtoseconds while the Gd atoms required five times as long to do so. That means the atoms were all briefly in parallel alignment, making the material strongly magnetized. "This is as strange as finding the north pole of a magnet reversing slower than the south pole," says Ilie Radu.

With their observation, the researchers have not only proven that magnetic reversal can take place in femtosecond timeframes, they have also derived a concrete technical application from it: "Translated to magnetic data storage, this would signify a read/write rate in the terahertz range. That would be around 1000 times faster than present-day commercial computers," says Radu.

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More information: Nature, DOI: 10.1038/nature09901 , 2011

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User comments : 6

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1 / 5 (1) Apr 13, 2011
to bad traditional disc storage mediums still use a rotating platter -- meaning that on you regular cheap harddrive you buy at best buy is bounded on the read write side purley by the spin speed, rotational speed, of the disc itself --- this article is therefore addressing SSD, or solid state drives that operate digitally meaning that the read write can be as fast as the closk speed of the controlling microprocessor on the ssd board. Which i believe is in the low Ghz range. Please double check me and comment.
3 / 5 (1) Apr 13, 2011
But wait... how would you store any information with this, if the state only lasts a few femptoseconds? I don't understand.
3 / 5 (1) Apr 13, 2011
But wait... how would you store any information with this, if the state only lasts a few femptoseconds? I don't understand.

Well, presumably the write head would be working that fast, and it would pass over a storage media (tape, disk, or something else,) changing the magnetic state of said media.
5 / 5 (1) Apr 13, 2011
this article is therefore addressing SSD

-SSDs are solid state drives. They're not magnetic, they are just a bunch of RAM chips.

But wait... how would you store any information with this, if the state only lasts a few femptoseconds? I don't understand.

-You misunderstood. The states don't last femtoseconds, they last decades. What lasts femtoseconds is the CHANGE of states. So, to go from on to off or visa versa takes femto seconds while the on or off state lasts indefinitely, for all intense and purposes.
-They aren't proposing a new type of storage or any new theory regarding storage. But what they have done is very important and could increase performance. They've measured the time required to store a bit and found that the time varies depending on the element used (undoubted the more massive elements take longer since it takes more energy to flip them). Now we can start picking the fastest switching elements, spin speed is still limited --> more heads=solved.
not rated yet Apr 13, 2011
circular polarized light, nice. Will only work in 2D.
not rated yet Apr 14, 2011
This means a giant hard drive with a 100 foot diameter disk in a vacume traveling at the speed of sound at the outer edge could store the planets data and access it at main frame speeds using muliple GMRD read/write heads.

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