Enhancement of exchange bias and ferromagnetic resonance frequency by using multilayer antidot arrays

Abstract

A systematic investigation of the dependences of the exchange bias and the ferromagnetic resonance frequency on the pore size of the antidot arrays fabricated by depositing Permalloy-FeMn multilayer thin films onto self-organized porous anodic aluminum oxide membranes was carried out. The magnetic and microwave properties of the antidot arrays with different pore sizes ranging from 30 to 80 nm are characterized and compared with that of the continuous thin films. It was found that the exchange bias field and the ferromagnetic resonance frequency are increased with the increase of the pore size, which may tentatively be interpreted in the framework of the random field model. It was also found that by using the antidot arrays in the best condition (the FeNi thickness is 20 nm and the pore size is 80 nm), one can enhance the exchange bias field from 65 to 135 Oe and the ferromagnetic resonance frequency from 3.1 to 4.1 GHz accordingly. © 2008 American Institute of Physics.