High-frequency modes in magnetic spectra of carbonyl iron

Magnetic spectra of composites filled with carbonyl iron powder were measured at frequencies of up to 30 GHz. Two previously unknown intensive high-frequency peaks of magnetic absorption have been found at frequencies surpassing the ferromagnetic resonance frequency. The peaks may be attributed to Aharoni exchange resonance modes. The resonances are excited inside magnetically isolated nanocrystallites that constitute carbonyl iron grains. Features of homogeneous ferromagnetic resonance in carbonyl iron powder grains are also discussed.