Abstract
Using measurements of the spectra of microwave-frequency resistance oscillations, we determine the room-temperature phase diagram of magnetic excitations caused by torques from dc spin-polarized currents in (thin permalloy)/copper/(thick permalloy) multilayer samples. We extend the measurements to larger values of current than have been reported previously. We find several additional modes that we are able to identify with motion of the thick magnetic layer as well as the thin one. Peaks in the microwave spectra at multiple frequencies suggest that spatially nonuniform dynamical states can be important in some circumstances. We compare the experimental phase diagram with simple theoretical models and achieve a good qualitative agreement.
- Received 11 April 2005
DOI:https://doi.org/10.1103/PhysRevB.72.064430
©2005 American Physical Society