Microwave-assisted magnetization reversal and multilevel recording in composite media

Abstract

Microwave-assisted magnetic reversal (MAMR) is studied for media comprising exchange-coupled composite elements comprising soft and hard layers. Reversal in such elements occurs under substantially reduced reversal fields, microwave fields, and microwave resonant frequencies as compared to those for homogeneous elements. Reversal can occur in uniform modes as well as nonuniform domain wall assisted modes depending on the soft layer thickness. In addition, a multilevel MAMR scheme is suggested where the recording media comprise multiple levels of elements, with each level having a distinct resonant frequency. These levels are addressed individually by tuning the frequency of the microwave field.