Width of the ferromagnetic resonance line in an anisotropic magnet in misoriented resonance and scanning magnetic fields

Abstract

The physical cause of the change in the linewidth Δ H pp in films of anisotropic ferromagnets is the change in the orientation of the equilibrium magnetization M during the registration of the absorption line, as was shown in (2) and (3). The calculations performed in these works showed that the width of the FMR line Δ H pp increased with the deviation of the magnetic field from the anisotropy axis (directed along the normal to the film). The linewidth reaches maximum values in the vicinity of angles ϕ corresponding to the ranges of the fastest variation of the function H R ( ϕ ). The increase in the linewidth obtained in the above-cited works is related to the fact that they were concerned with a spe- cial case of orientation of the magnetic and scanning fields, namely, the fields were collinear. We may sup- pose that in the case of misorientated resonance and scanning fields the above mechanism of the linewidth variation will lead not only to a broadening but also, at certain angles, to a narrowing of the FMR line. Abstract —The dependence of the width Δ H β of the ferromagnetic resonance (FMR) line in anisotropic mag- nets on the angle of misorientation β between the static (resonance) and scanning magnetic fields was investi- gated both experimentally and theoretically. The change in the linewidth is due to the dependence of the equi- librium orientation of the magnetization vector on the direction of the magnetic field upon the passage through the resonance. Using iron garnet films as an example, it was shown that under such a misorientation (a nonzero angle β ) the linewidth is smallest. It was also shown that a two-dimensional representation of FMR spectra, in contrast to one-dimensional angular dependences of the resonance parameters, contains full information on the spectral characteristics of the film, including noncollinear field configurations. © 2002 MAIK "Nauka/Interpe- riodica".