Anneal-less Domain Wall Displacement Detection of 15 Gbit/in~2 land-groove recording using a deep groove substrate and a red laser

摘要

Domain Wall Displacement Detection (DWDD) medium with no annealing method, which we call "anneal-less" DWDD medium, has been improved for practical use. The key technologies of our progress are not only an optimum design of the magnetic film structure but also a deep groove substrate for land-groove recording with a quite unique groove form. The substrate was prepared by using the mastering process with a reactive ion etching (RE) method. We achieved 15 Gbit/in~2-areal density with wide system tolerances using the anneal-less DWDD medium, a 660nm-laser and a 0.60 NA objective lens. The areal density corresponds to 4.7 GB-capacity on a disc like MiniDisc~(TM) (MD) with a 64 mm-diameter.