Tailoring exchange coupling between magnetic nano-grains of high density magnetic recording media

摘要

Intergranular exchange coupling between magnetic nano-grains is one of important parameters to develop magnetic recording media towards the areal density of 1000 Gbits/in2. In this presentation, various processings, involving oxide co-sputtering for perpendicular media, spontaneous phase separation for longitudinal media, and grain boundary (GB) diffusion derived from underlayer or overlayer to induce tunable exchange coupling, have been reviewed to tailor the exchange coupling, including their main principles, present achievements and engineering challenges. Much attention is paid to the physical origin of magnetically induced phase separation of Co-Cr-based alloy, which governs media noise and coercivity, and its applications to the longitudinal media. A proposal of GB diffusion is also highlighted in detail to show a feasibility to tailor the exchange coupling, including calculation results and experimental evidences.