IBM claims spintronics memory breakthrough

Researchers still face significant hurdles before a memory product can be manufactured

By Lucas Mearian

August 12, 2012 01:58 PM ET

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Computerworld - In a paper set to be published this week in the scientific journal Nature, IBM researchers are claiming a huge breakthrough in spintronics, a technology that could significantly boost capacity and lower power use of memory and storage devices.

Spintronics, short for "spin transport electronics," uses the natural spin of electrons within a magnetic field in combination with a read/write head to lay down and read back bits of data on semiconductor material.
By changing an electron's axis in an up or down orientation - all relative to the space in which it exists -- physicists are able to have it represent bits of data. For example, an electron on an upward axis is a one; and an electron on a downward axis is a zero.
Spintronics has long faced an intrinsic problem because electrons have only held an "up or down" orientation for 100 picoseconds. A picosecond is one trillionth of a second (one thousandth of a nanosecond). One hundred picoseconds is not enough time for a compute cycle, so transistors cannot complete a compute function and data storage is not persistent.

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In the study published in Nature, IBM Research and the Solid State Physics Laboratory at ETH Zurich announced they had found a way to synchronize electrons, which could extend their spin lifetime by 30 times to 1.1 nanoseconds, the time it takes for a 1 GHz processor to cycle.
The IBM scientists used ultra short laser pulses to monitor the evolution of thousands of electron spins that were created simultaneously in a very small spot, said Gian Salis, co-author of the Nature paper and a scientist in the Physics of Nanoscale Systems research group at IBM Research.
Usually, such spins find electrons randomly rotating and quickly losing their orientation. In this study, IBM and ETH researchers found, for the first time, how to arrange the spins neatly into a regular stripe-like pattern -- the so-called persistent spin helix.
The concept of locking the spin rotation was originally proposed as a theory back in 2003, Salis said. Since then, some experiments found indications of such locking, but the process had never been directly observed until now, he added.
"These rotations of direction of spin were completely uncorrelated," Salis said. "Now we can synchronize this rotation, so they don't lose their spin but also rotate like a dance, all in one direction."
"We've shown we completely understand what's going on there, and we've proven that the theory works," he added.

Helical spin modes and the persistent spin helix (PSH). a, The spins of the two helical spin modes É+ and É- rotate with opposite helicity as the electron moves along y. The Sz(y) of the two modes is the same. b, Spins precess about an external magnetic field Bx such that the É+ mode is shifted towards -y if Bx < 0 is applied. c, d, Maps of Sz(y,t) show the time evolution of the PSH for Bx = 0 (c) and Bx = -1T (d). Sz(y) oscillates in both cases, but for Bx = -1T, the position of constant phase, y0, is shifted with t (marked by the dashed line). Source: Nature Physics/IBM Research Zurich