Compositional microstructures of CoCr-alloy perpendicular magnetic recording media

Compositional microstructures of CoCrTa and CoCrPt perpendicular magnetic recording media are investigated using a high resolution transmission electron microscope equipped with an imaging filter. In the CoCrTa film, clear Cr segregation at grain boundaries is recognizable. The Cr-enriched layer is analyzed to be paramagnetic phase of which Cr concentration is greater than 30 at%. In the case of CoCrPt film, Cr segregation is observed within the grains, and the Cr contents at grain boundaries are far lower than those measured for the CoCrTa film. The difference in the compositional microstructure is related to the difference in noise characteristics of CoCrTa and CoCrPt media.