A method of measuring anisotropy field of polycrystalline thin-film media

Ferromagnetic resonance (FMR) is used to measure the magnetic anisotropy fi eld H-k and its dispersion of poly-crystalline recording media. This method does not use any single crystal substrate. A high-intensity field is appli ed vertically to a sample surface to completely saturate the magnetization and a high-frequency (over 50 GHz) magnetic field is applied in the surface . An FMR simulator based on the Landau-Lifshitz-Gilbert equation confirms t hat the magnetic (exchange and/or magnetostatic! interactions have very lit tle effect on the resonant frequency in the configuration used. The linewid th of the FMR spectrum is affected by the H-k dispersion and damping consta nt. Methods using a torque or magnetization curve include magnetic interact ions, resulting in a systematic error to the value of H-k. This FMR method is applied to CoCrPt-alloy thin-film media with a Cr-alloy underlayer grown on a glass substrate. A conventional torque method is also used for compar ison. The axis of hexagonal-close-packed Co magnetic grain is distributed a t random in the surface. In an FMR measurement, external magnetic field is applied vertically to the surface up to 55 kOe for two frequencies (71 and 117 GHz). The obtained H-k is 7.0+/-0.2 kOe, which is a little higher than the H-k of 6.4 kOe estimated with the torque loss method. Important physica l parameters that affect the recording performance are also estimated using the linewidth of FMR spectra for different frequencies with a micromagneti c simulation: H-k dispersion=1.2+/-0.5kOe, Gilbert's damping constant alpha =0.03+/-0.01, and a g value=2.19+/-0.02. (C) 1999 American Institute of Phy sics. [S0021-8979(99)52108-7].