Thermally Excited Spin Waves of NiFe Nano-ring Arrays on Anodic Aluminum Oxide Templates

Abstract

The patterned substrates have been widely developed for various applications in the nanotechnology. In particular, the magnetic ring arrays could be utilized to not only the magnetic devices, such as memories and logics, but also magnetic stealth films using spin wave excitations. In this works, the magnetic switching behaviors and the thermally excited spin wave properties of the NiFe (permalloy) ring arrays on the anodic aluminum oxide template with carbon nanotubes were investigated. With increasing the diameter of the rings, the larger dipole interactions induced the larger coercive field of the array films in the plane directions. At the magnetically saturation conditions, the smaller diameter of the rings produced the single and broad spin wave absorptions due to the isotropic magnetic domains in both the horizontal and the vertical directions. When the size of the ring increased, each component felt different magnetic anisotropy field so that the two spin wave excitation peaks revealed. In terms of the mass production of the magnetic nano-ring arrays on the anodic aluminum oxide template, the various size and the shapes of the magnetic ring patterns could be good candidates for the rf stealth films of the defense industries.