Ferromagnetic resonance frequency of a thin Mo-permalloy film

There is great interest both in the magnetic recording and wireless phone i ndustries in the development of magnetic films with permeabilities that rea ch out into the GHz frequencies. In order to obtain such films the understa nding of the frequency response of the ferromagnetic resonance of basic mat erials is needed. In this study the permeability of a thin film of Mo perma lloy is measured up to 3 GHz utilizing a strip loop device. The effect of a n externally applied field (H-dc) along the easy axis and hard axis on the transverse bias permeability as a function of frequency is measured through resonance. The full width at half maximum (Delta f ) of the imaginary part of the permeability at resonance which is related to resonance damping is also measured. It is found that in the vicinity of H-dc-H-k near zero, Delt a f increases with decreasing dc field. This phenomenon is explained in ter ms of the Hoffmann ripple theory. (C) 2000 American Institute of Physics. [ S0021-8979(00)28408-9].