Dipolar induced, spatially localized resonance in magnetic antidot arrays

Abstract

Dipole induced, spatially localized ferromagneticresonances (at 35 GHz) are observed in micron-sized antidot arrays in permalloyfilms fabricated with photolithography. All square (3 μ m ×3 μ m ) and rectangular (3 μ m ×4, 5, and 7 μm) array samples exhibit double resonances, with each resonance possessing uniaxial in-plane anisotropy. Interestingly, the easy axes of the two resonances are orthogonal in all cases. The magnitude of the induced dipolar anisotropy decreases with increasing rectangular aspect ratio for one of the resonances, but remains essentially constant for the other. Micromagnetic simulations reveal that the two resonance peaks are the consequence of a dipole field distribution producing two areas with distinctly different demagnetizing field patterns.