Multilayer exchange spring media for magnetic recording

Abstract

The concept of exchange spring media is extended from two layers to N layers. The coercive field of the multilayer structure decreases with 1∕N while the energy barrier is only determined by the magnetic properties of the hardest layer. A 25nm thick trilayer has a 7.5 times smaller coercive field (1.4T) as a single layer at the same thermal stability and for the same value of the magnetization. A continuous variation of the anisotropy in the recording media reduces the coercive field by a factor of 10 for a layer thickness of 25nm.