Microwave transmission through ferromagnetic metals

Transmission of microwave radiation through a metal ferromagnet is enhanced at the field corresponding to ferromagnetic antiresonance. This phenomenon can be used to measure the magnetic parameters of a specimen. It is a particularly useful and sensitive tool for studying the damping processes in metals. This technique is compared with that of ferromagnetic resonance absorption (FMR). It is pointed out that the FMAR transmission method is complimentary to the FMR method when non-local (i.e. wave-number dependent) effects are important, because the spatial variation of the RF magnetization and fields is much greater at FMR than at FMAR. This point is illustrated using experiments on nickel for which the damping parameter measured using FMAR is larger than that measured using FMR at temperatures less than 300K.