Effects of boron addition to underlayer for CoCrPt media on magnetic characteristics and microstructure

Magnetic and recording characteristics of CoCrPt media with a CrTiB underlayer was investigated. Higher coercivity Hc and coercive squareness S* were obtained compared with the media that had a CrTi underlayer. The overwrite property of the media was also improved by adding boron, while the change in media noise was very small. Transmission electron microscopy analysis showed that the crystal grain-size dispersion in the magnetic layer was reduced by about 15% when boron was added to the underlayer, and the average grain size was almost the same as when the CrTi underlayer was used. The higher S* and improved overwrite property that resulted when using a CrTiB underlayer should be attributed to the reduction in the grain size dispersion, which provides a narrower switching field distribution.