Spin-Torque Ferromagnetic Resonance Measurements of Damping in Nanomagnets

Abstract

We measure the magnetic damping parameter a in thin film CoFeB and permalloy (Py) nanomagnets at room temperature using ferromagnetic resonance driven by microwave frequency spin-transfer torque. We obtain ${\alpha }_{CoFeB}=0.014\pm 0.003$ and ${\alpha }_{Py}=0.010\pm 0.002$, values comparable to measurements for extended thin films, but significantly less than the effective damping determined previously for similar nanomagnets by fits to time-domain studies of large-angle magnetic excitations and magnetic reversal. The greater damping found for the large amplitude nanomagnet dynamics is attributed to the nonlinear excitation of non-uniform magnetic modes.

13 pages, 2 figures

References in corpus (4)

• Spin-transfer-driven ferromagnetic resonance of individual nanomagnets
• Excitations of incoherent spin-waves due to spin-transfer torque
• Large-amplitude coherent spin waves exited by spin-polarized current in nanoscale spin valves
• Theory of the spin-torque-driven ferromagnetic resonance in a ferromagnet/normal-metal/ferromagnet structure

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• Spin-torque driven ferromagnetic resonance of Co/Ni synthetic layers in spin valves
• Phase-resolved electrical detection of coherently coupled magnonic devices
• A versatile rotary-stage high frequency probe station for studying magnetic films and devices
• Local spin transfer torque and magnetoresistance in domain walls with variable width