Extremely High-Density Longitudinal Magnetic Recording Media

TLDR

Areal‑density gains in magnetic recording hinge on producing low‑noise, granular thin‑film media that remain thermally stable, requiring grains small enough to be magnetically isolated yet large enough to withstand write‑field limits of about 10–12 nm; current CoCr alloys are near this limit, so further density increases demand grain size reduction and harder materials. This review focuses on the materials and fabrication strategies that enable extremely high‑density longitudinal magnetic recording media. The authors examine thermal stability, write‑coercivity constraints, and alternative media designs aimed at achieving densities above 40–100 Gbits/in².

Abstract

▪ Abstract Areal density progress in magnetic recording is largely determined by the ability to fabricate low-noise, granular thin lm media with sufficient stability against thermal agitation to warrant long-term data storage. A key requirement is a medium microstructure with small, magnetically isolated grains to establish optimal macro- and micro-magnetic properties. A lower bound for the minimal average grain diameter, compatible with thermal stability, is imposed by the write field capability of the recording head. It is 10–12 nm assuming maximal writeable coercivities of 400 kA/m (5000 Oe). These are already achieved in today's state-of-the-art CoCr-based thin lm alloy media, leaving little room for further improvements and density gains based on continued grain size reduction. A threefold reduction in grain diameter, however, translating into a tenfold increase in areal density is theoretically possible if write field constraints can be overcome, allowing utilization of magnetically harder alloys. This review emphasizes materials and fabrication aspects behind media for extremely high-density longitudinal magnetic recording. Special attention is paid to thermal stability and write coercivity constraints. Various alternative media designs for extremely high-density recording beyond 40–100 Gbits/inch 2 are reviewed.