Influence of patterning fluctuation on read/write characteristics in discrete track and bit patterned media

• Published in: Journal of magnetism and magnetic materials Vol. 320; no. 22; pp. 2935 - 2943
• Main Authors: Hashimoto, Mitsuhiro, Miura, Kenji, Muraoka, Hiroaki, Aoi, Hajime, Wood, Roger, Salo, Michael, Ikeda, Yoshihiro
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2008; Elsevier
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronics; Exact sciences and technology; General theory and models of magnetic ordering; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Magnetic fluctuation; Magnetic properties and materials; Media noise; Patterning fluctuation; Perpendicular magnetic recording; Physics; Recording and replay of audio and video signals; Scanning probe microscopes, components and techniques; Storage and reproduction of information; 85.70.Kh; 85.70.Ay; Media noise; Magnetic fluctuation; Perpendicular magnetic recording; Patterning fluctuation; Performance evaluation; Scanning electron microscopy; Fluctuations; Patterning; Magnetization; Magnetic cluster; High density; Magnetic model; Roughness; Line widths; Background noise; Cluster model; Defects; Standard deviation; Modelling
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2008.08.063

The read/write characteristics of non-patterned media (NPM), discrete track media (DTM), and bit patterned media (BPM) are examined by modeling the magnetization distribution of NPM and patterning fluctuation of DTM. By comparing spin-stand measurement with calculation, the magnetization distribution of NPM was well characterized with a new Voronoi cell magnetic cluster model, in which the cluster size at the track edge, 〈 D edge〉, was larger than that at the track center, 〈 D center〉 by a factor of two. Based on an analysis of patterning fluctuations seen in SEM images of DTM, line-edge roughness (LER) was modeled as a long-wavelength center-line roughness (CLR) plus a short-wavelength line-width roughness (LWR). It was confirmed that the standard deviation of the patterning fluctuation was much smaller than that of the magnetic fluctuation for NPM. This allowed DTM to achieve higher off-track performance than NPM. By examining the 747 curves, it was revealed that DTM could have an advantage in track-density of up to approximately 25% assuming patterning fluctuations can be well controlled at high track density. In BPM, fabricating accurate dots is essential. The relationship between dot defect rate and patterning fluctuation was examined, and the maximum allowable standard deviation of LER was derived as 2 nm for achieving 1 Tbspi.