Spin-torque ferromagnetic resonance measurements of damping in nanomagnets

The authors directly measure the magnetic damping parameter alpha in thin-film CoFeB and Permalloy (Py) nanomagnets at room temperature using a recently developed ferromagnetic resonance technique where the precessional mode of an individual nanomagnet can be excited by microwave-frequency spin-transfer torque and detected by the giant magnetoresistance effect. The authors obtain alpha(CoFeB)=0.014 +/- 0.003 and alpha(Py)=0.010 +/- 0.002, values comparable to measurements for extended thin films, establishing that patterned nanomagnets can exhibit magnetic damping that is consistent with that of unpatterned bulk material. (c) 2007 American Institute of Physics.