Chemical segregation in CoNiPt(SiO2) alloy film

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Abstract
Chemical segregation in SiO2‐added CoNiPt alloy films for high‐density longitudinal recording media have been studied by high‐resolution transmission‐electron microscopy‐energy dispersive spectroscopy with a spatial resolution of 20 Å. Sputtered CoNiPt(SiO2) films consist of well‐separated grains with diameters less than 200 Å. Si is clearly detected only in a grain boundary region with the width from 12 to 30 Å. Oxygen concentration in the grain boundary is also much higher than that inside the grain. X‐ray photoelectron spectroscopy shows that Si atoms in the film are in the form of SiO2. Therefore, it is concluded that SiO2 is segregated to the grain boundary in the CoInPt films. The development of the grain separation due to this chemical segregation explains the excellent magnetic and recording properties of the CoInPt(SiO2) films, such as high coercivity beyond 2400 Oe and low media noise. Inhomogeneity of CoNiPt alloy elements are also discussed.