Co-Cr-W-C alloy thin films for perpendicular recording media

Highly durable Co-based alloy films suitable for perpendicular magnetic recording media were obtained by sputtering technique. These alloy films consist of Co, Cr, W, and C with a weight composition of Co: Cr: W: C = 68 : 26 : 5 : 1, one of typical compositions of a group of alloys called stellite. These sputtered alloy films showed ferromagnetism in contrast to the weakly magnetic bulk stellite alloy and high perpendicular magnetic anisotropy. No magnetism was found on the corresponding alloy films with no C atoms. The durability of the Co-Cr-W-C alloy films to ring-shaped head abrasion was very high compared with usual Co-Cr films. The films were also chemically stable in marked contrast to Co-Cr films. An aggregated structure with very fine granules was found in the TEM microphotograph of an ion-etched Co-Cr-W-C alloy film, in marked contrast to the coarse grain structure in Co-Cr alloy films. Existence of carbides which may mainly consist of tungsten carbides was found in the Co-Cr-W-C films. The carbides, which must be segregated from the Co-Cr alloy phase, are responsible for the remarkable properties of Co-Cr-W-C alloy films.