Recording Tiny Marks on a Magneto-optical Medium with Micro-Columnar Structure

Abstract

The MsHc value of TbFeCo magneto-optical (MO) film has been identified as a key factor in high-density recording. A particular microstructure formed in the magneto-optical memory layer due to the magnetic underlayer was found to be effective for increasing the MsHc value in 160 nm thick TbFeCo recording film. However, a thinner memory layer is required for high performance of productivityThis paper describes the relationship between magnetic properties and the micro-columnar structure, which depends on the thickness of the TbFeCo recording film and its layer structureIt has been found that a thickness of more than 100 nm in the memory layer produced by sputtering from an alloy target is needed for the DWDD method. And there is some difficulty in recording a tiny mark on the 50 nm thick memory layer in a multi-layer MO mediumHowever, the static magnetic properties of the memory layer are not altered by differences in thickness. As much as 1.8 ×106 erg/cm3 Ku can be obtained by sputtering a thickness of less than 80 nm from an alloy target, and it is possible to perform ultra-high density recording in an 80 nm thick memory layer with a mark length of less than 50 nmThese results suggest that control of the exchange coupling boundary between the layers in a multi-layer MO mediummakes it possible to record stable tiny marks.