Local modes and two magnon scattering in ordered permalloy antidot arrays

Antidot arrays consisting of periodically arranged holes in continuous magnetic films exhibit periodic demagnetization field distributions, which have large impact on the magnetic structure and properties such as enhanced coercivity. The authors report on the investigation of the statics and the dynamics of ordered square antidot arrays with 180 nm period and 70 nm antidot diameter that have been prepared by vapor deposition of 20 nm Permalloy on porous anodic alumina substrates. Using superconducting quantum interference device magnetometry, magneto-optical Kerr effect measurements and angular variable ferromagnetic resonance (FMR) spectroscopy at 9.2 GHz, together with micromagnetic simulations several local magnetization modes, were identified. The enhanced FMR linewidth with increasing out-of-plane angle of the magnetic field is not due only to demagnetization effects, but is rather attributed to two magnon scattering processes. This feature is assumed to originate from the surface roughness [w(rms)(L=1.3 mu m) similar to 5 nm] of the alumina substrate which is quantified by atomic force microscopy. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3076144]