High density recording characteristics of sputtered γ-Fe2O3 thin-film disks

Abstract

Sputtered γ‐Fe₂O₃ thin films are attractive in practical application to high density magnetic recording. This paper presents basic processes of γ‐Fe₂O₃ thin‐film fabrication, magnetic properties, and high density recording characteristics of the films. The film is prepared by reactive sputtering of an iron alloy containing a small amount of Co, Ti, and/or Cu in an Ar‐O₂ atmosphere on anodized Al alloy substrates and successive heat treatment. The film shows a high coercivity of 1000 Oe and a coercive squareness of 0.84 with the reduced thickness. The anodized Al alloy provides hard, smooth, and chemically stable substrates. The continuous γ‐Fe₂O₃ thin films show high recording density with an excellent signal to noise ratio (SNR). First, the recording characteristics of the film employed in practical disk storage with the areal recording density of 24 000 bit/mm² are described. SNR improves as the average crystallite size decreases. It is shown that 35 dB can be obtained at the linear density of 1000 flux reversals/mm with the track width of 10 μm. Finally, the density D_6dB of 2600 flux reversals/mm is experimentally shown by using a Mn‐Zn ferrite head with the small gap length of 2g = 0.15 μm operated at the heat‐medium spacing of 0.1 μm.