Effect of carbon overcoat implantation on the magnetic and structural properties of perpendicular recording media

Carbon overcoats play an important role in the corrosion protection of recording media used in hard disk drive technology. For achieving high areal density, there is a need to reduce the magnetic spacing. Since Carbon overcoat thickness is one of the major contributors to the spacing, it is essential to design suitable overcoats that can protect the media even when they are thin. Filtered cathodic vacuum arc (FCVA) has been studied in the past as potential media overcoat. In order to achieve desired property of FCVA carbon, it is essential to apply a suitable bias voltage, which results in an energetic carbon deposition on the magnetic layer of the recording media. We have recently reported the preliminary results of damage caused on antiferromagnetically coupled (AFC) media layer based on XPS and some magnetic characterization techniques. In this paper, we focus our attention on the implantation effects of energetic carbon on the magnetic and structural properties of recording media of two types; AFC and a single layer, in order to gain more meaningful insight on the implantation and its effect. The recording media samples were prepared at room temperature by dc magnetron sputtering using Intevac Lean 200B production type sputtering tool. The schematic illustration of the two types of samples in this study is shown. In single layered (SL) sample, the magnetic layer had a thickness of 4.5 nm. In AFC sample, the 4.5 nm magnetic layer was antiferromagnetically coupled to another magnetic layer of thickness 12 nm through a thin Ru layer. Samples were prepared without the soft underlayers for characterization using alternating gradient magnetometry (AGM). Typical seedlayers of perpendicular media were used. The carbon overcoat using FCVA was deposited using double bend DC filtered cathodic vacuum arc (FCVA). To control the deposition ion energy, DC negative bias was applied to the substrate during the deposition.