Ferromagnetic resonance linewidth in metallic thin films: Comparison of measurement methods
Sangita S. Kalarickal, Pavol Krivosik, Mingzhong Wu, C E. Patton, Michael L. Schneider, Pavel Kabos, Thomas J. Silva, John P. Nibarger
Strip line (SL), vector network analyzer (VNA), and pulsed inductive microwave magnetometer (PIMM) techniques were used to measure the ferromagnetic resonance (FMR) linewidth for a series of Permalloy films with thicknesses of 50 and 100 nm. The SL-FMR measurements were made for fixed frequencies from 1.5 to 5.5 GHz. The VNA-FMR and PIMM measurements were made for fixed in-plane fields from 1.6 to 8 kA/m (20-100 Oe). The results provide a confirmation, lacking until now, that the linewidths measured by these three methods are consistent and compatible. In the field format, the linewidths are a linear function of frequency, with a slope that corresponds to a nominal Landau-Lifshitz phenomenological damping parameter α value of 0.007 and zero frequency intercepts in the 160-320 A/m (2-4 Oe) range. In the frequency format, the corresponding linewidth versus frequency response shows a weak upward curvature at the lowest measurement frequencies and a leveling off at high frequencies.