Influence of recording field direction on linearity of transition in hard disks with stacked structure

Reducing the transition noise is one of important issues in order to achieve higher recording density in hard disks (HDs). The recording layers of commercial HDs have stacked structure consisting of a layer without oxygen (the upper layer) and a granular layer with oxygen (the lower layer) [1]. The domain structure of the recording layer demagnetized with perpendicular magnetic field differs from that demagnetized with in-plane field [2], [3]. In this study, we clarify the influence of recording field direction on the linearity of the transition and discuss the relation between the transition and the demagnetized domain structure.