Dynamical States in Nanomagnets Driven by Spin-Transfer Torques
Abstract
A spin-polarized current passing from a normal metal (N) to a ferromagnet (F) can deposit spin angular momentum into the magnet, thereby applying a torque to its moment. Using nanoscale F/N/F trilayer devices, we have recently demonstrated that spin-transfer torque from a constant current can drive the moment of a nanomagnet into several different steady-state dynamical modes, thereby causing the resistance of the sample to oscillate at microwave frequencies. Here we describe more detailed investigations of these phenomena. The relative size of the first and second harmonics of the microwave signal changes as we turn the angle of an applied magnetic field relative to the sample's easy axis, confirming that the signals arise simply from the sample resistance and not an inductive coupling. We compare the dynamics of cobalt nanomagnets to those made from permalloy, which exhibit smaller magnetic moments and more uniform magnetic anisotropy. Finally, we describe the dependence of the dynamical signals on temperature.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARA23007S