Multi-peak ferromagnetic resonance in Co nanowires array

Ferromagnetic resonance in an array of Co nanowires electrolytically deposited into nanoporous alumina template is investigated at four microwave frequencies in the range from 9.3 to 69.7 GHz. The array consists of highly textured hcp Co with hexagonal axes perpendicular to the nanowires. The spectra measured at higher frequencies can be decomposed into four wide resonances peaks. Different mechanisms, which can lead to the multi-peak resonance, are discussed.