Ferromagnetic Resonance Study of Square-Array Antidot Permalloy Thin Films

separated dot, which is typically smaller than a normal magnetic domain, will be one bit of information.Antidot arrays may also be a candidate for magnetic information storage.It turns out that the introduction of the holes produce a greatly modified domain structure and creates laterally separated domains, which may act as a bit.The magnetic dot arrays have received the most attention recently.Previous experiments show that in magnetic dot arrays, in contrast to the sheet film, there is an induced in-plane magnetic anisotropy that is strongly dependent on the array symmetry 1,2 .Knowledge of how the dot array symmetry affects the in-plane anisotropy will allow the fabrication of a magnetic sample with finely tuned desired anisotropy energy.In contrast to a sheet film, ferromagnetic resonance (FMR) studies show the presence of additional resonance peaks along with the uniform precession mode.This knowledge sheds light on the non-uniform magnetization of the sample and the dipole coupling between neighboring dots.2,3 Though there is much literature on the properties of magnetic dots, literature on antidot arrays is scarce, especially FMR studies.It is with this in mind that we undertook an investigation of the induced properties of antidot arrays in Permalloy thin films.A previous experiment on this subject shows additional magnetic anisotropy energies and a completely modified domain structure.4 Our work describes the ferromagnetic resonance spectra of three antidot samples each with square antidot array symmetry but with varying lattice spacing.As with the magnetic dot arrays, the FMR spectra shows peaks in addition to what would be expected for uniform precession.These extra peaks may be attributed to higher order two dimensional spin wave modes that travel parallel to the film plane.