EXPERIMENTAL-OBSERVATION OF SOLUTE SEGREGATION IN LONGITUDINAL COPTCR/CR MAGNETIC THIN-FILMS

The grain boundary structure and elemental segregation in longitudinal Co75P12Cr13/Cr magnetic thin film media were investigated by using high resolution transmission electron microscopy and nanoprobe X-ray chemical analysis. The present study provides experimental evidence for the segregation of Cr and possibly Pt as wed along the high-angle. grain boundaries of Co-alloy grains. The maximum extents of Cr and Pt segregation are reported in terms of Cr/Co peak ratios and Pt/Co peak ratios measured at four grain interior locations and five grain boundary locations. The average Cr/Co peak ratios were 1.35 +/- 0.64 for the grain boundary and 0.51 +/- 0.16 For the grain interior. The average Pt/Co peak ratios were 1.10 +/- 0.22 for the grain boundary and 0.95 +/- 0.14 for the grain interior. As the extended excitation region and the electron beam broadening during transmission are larger than the boundary width, the actual segregation will be even higher than the values shown here. This nonmagnetic elemental segregation along the boundary appears to be related to reduced magnetic exchange coupling between neighboring grains and to the low media noise characteristics observed in longitudinal CoPtCr ahoy thin films with ultra-thin Cr underlayers.