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Spin-Transfer Control of High Resistance Magnetic Bits

Computer memory chips that are simultaneously fast, high-density, and non-volatile (able to store information without being connected to a power source) would enable revolutionary improvements in computing and communications technologies, including "instantly-on" computational devices. The leading technology under development involves information storage with nanometer-scale magnets. (A nanometer is a billionth of a meter). The electrical resistance of a device consisting of two such nanomagnets depends on the relative orientation (parallel or anti-parallel) of the magnets. The most efficient way to write information to these magnetic bits, that is to switch their magnetic orientation, would be a direct "spin-transfer" process from a current made up of spin-polarized electrons, that is electrons which all have their individual magnetic moments pointing in the same direction. When these electrons flow through a nanomagnet they can "transfer spin" to the nanomagnet and thus cause it to reverse the direction of its magnetic poles. However, up to now this method has faced a key obstacle -- previous devices had low resistances, 1-10 Ohms, while 1,000-10,000 Ohms are required to be compatible with silicon electronics. We have recently achieved this milestone. By incorporating an aluminum oxide barrier only a few (4-5) atoms thick between two magnetic layers, we demonstrated a resistance of 2,000 Ohms in a working spin-transfer-driven nanomagnetic memory bit.

[Lead CNS Investigators: R. A. Buhrman and D. C. Ralph]

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