FMR SPECTRA OF ORIENTED GAMMA-FE2O3, CO-GAMMA-FE-2, O-3, CRO2, AND MP TAPES

Ferromagnetic resonance spectra have been measured at 34.5 GHz on oriented gamma-Fe2O3, Co-gamma-Fe2O3, CrO2 and MP tapes. Particle orientation distribution functions were determined by measuring the angular dependence of remanence. The distribution functions were used to calculate FMR spectra using the Landau-Lifshitz equation and the method of Netzelmann. The anisotropy energy, packing fraction and damping constant were adjusted in order to fit the data. The values of the damping constants obtained from the fits ranged from a low of 0.051 for CrO2 to a high of 0.92 for MP. These values, including previously measured damping constants for Ba-ferrite, correlate well with the switching speed measurements of Doyle and co-workers, which show CrO2 to be the slowest and MP the fastest.