Ferromagnetic resonance mode interactions in periodically perturbed films

Abstract

Ferromagnetic resonance linewidth measurements are reported for thin films of Ni80Fe20 deposited on substrates with 320 nm period grooves or parallel aperiodic scratches. These films are model systems for studying the effects of inhomogeneity on ferromagnetic resonance. With the grooved substrate, the ferromagnetic resonance spectra show that interactions split the resonant frequencies of interacting modes leading to two resonances for strong interactions and broadened resonances for weak interactions. The results obtained with the scratched substrate are in agreement with the two-magnon model of linewidth, showing sharply increased linewidth when the scratches are oriented to allow coupling to degenerate spinwave modes. The results are not in agreement with a simple model of linewidth as a direct measure of the spread in local resonance fields.

Splitting of spin-wave modes in thin films with arrays of periodic perturbations: theory and experiment

“…This behavior, i.e. the existence of additional branches in the FMR spectra, has been discussed by some authors in periodically modulated films [15,16,18,19]. So far we have not mentioned anything about the shape of the perturbations.…”

“…Typical MCs that are currently being investigated include (i) hybrid structures composed by alternating materials [5][6][7][8][9], (ii) dipolarly coupled nanowire arrays [10][11][12], (iii) nanostripes with periodically varying width [13], (iv) antidot lattices [4,11,[14][15][16] and (v) thin films with 1D and 2D arrays of periodic perturbations [17,18]. Periodic defect structures do not necessarily need to be of geometrical type, like magnetic films on a grooved [19,20] or ripple substrate [21], but can consist of a variation of the magnetic parameters, i.e. a periodic modulation of the saturation magnetization M s , as created by ion implantation [17].…”

Localized Ferromagnetic Resonance in Inhomogeneous Thin Films

“…The two-magnon model of linewidth [18][19][20][21][22][23][24], reviewed below, accounts for interactions through the spin wave dispersion relation and treats the inhomogeneity as a perturbation. Two-magnon and local resonance linewidths behave very differently, but the two-magnon model has also been verified by a different set of experimental results [18,25,26].…”

Hamiltonian formalism for two magnon scattering microwave relaxation: Theory and applications

“…16 Their model involved scattering from regularly shaped surface defects due to both dipole fields and surface anisotropy, and it specifically addressed the situation for ultrathin films. The model predictions have been tested experimentally by Lindner et al 27 and McMichael et al, 28 for example. Recently, McMichael and Krivosik presented a detailed classical model of TMS relaxation for localized randomly distributed inhomogeneities.…”