Effects of very thin carbon seedlayer on formation of hcp phase for CoCrPtB/Co60Cr40 perpendicular magnetic recording media

This paper reports on a significant improvement of magnetic properties for CoCrPtB/Co₆₀Cr₄₀ perpendicular recording media by utilizing a very thin C seedlayer even with a thickness of less than 1 nm. This is caused by the following microstructural characteristics: 1) the C seedlayer, heated to above 200°C, reacts with the CoCr intermediate layer, resulting in the formation of a nanocrystalline layer with a thickness of about 6 nm; 2) Cr-deprived hcp grains with Cr segregation structure grow on the nanocrystalline layer without forming σ-phase grains in the intermediate layer; 3) CoCrPtB magnetic layers grow epitaxially on the intermediate layer without forming an initial layer, which behaves as a soft ferromagnetic layer and degrades magnetic properties of the media.