Fine Grained Ni-Zn Ferrite-Plated Backlayers for Co-Cr-Ta Perpendicular Magnetic Recording Media

Abstract

Co-Cr-Ta perpendicular magnetic recording media with Ni-Zn ferrite backlayers are promising candidates to improve high frequency performance in extremely high linear density applications. Though ferrite plating facilitates to fabricate polycrystalline Ni-Zn ferrite films even at low temperature below 100 QC, the films have disadvantages oflarge grain size (200~300 nm) and roughness (4~5 nm). Such surface texture caused aggregating grains without clear magnetic isolations in Co-Cr-Ta layers deposited on them, resulting in low perpendicular coercivity Hd (1.3 kOe). These properties will lead poor recording density characteristics and high media noise. RF sputter-etching of the Ni-Zn ferrite backlayers was attempted in order to improve their surface texture. It reduced grain size (30~50 nm), and increased Hd (3.0 kOe) in the Co-Cr-Ta layers, presumably through a reduction of surface roughness and a formation of many fine nodules on the Ni-Zn ferrite-plated backlayers, which play a role of nucleation sites for the Co-Cr-Ta grains.