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Nanomagnetics: Microwaves from Nanomagnets

The ability to control the configuration of nanoscale magnetic elements is central to future information storage technologies, such as magnetic random access memory. CNS nanomagnetics researchers have discovered a new mechanism referred to as “spin transfer” where a spin-polarized electron current provide much stronger torques to control a nanomagnet’s orientation than can the usual approach of applied magnetic fields. Spin transfer is additionally interesting because of predictions that it may be able to drive types of very-high-frequency precessional motion that simple magnetic fields cannot. We have recently made the first direct measurements of the dynamics of this effect as nanomagnets rotate more than 10 billion times a second. A simple steady current excites high-speed magnetic precession in the magnetization (M) of cobalt (Co) nanomagnets, by balancing the spin transfer torque against a magnetic damping force. The CNS group is now working to produce nanometer-scale microwave sources for high-speed signal processing.

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

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