Improved grain isolation of Co/sub 80/Pt/sub 20/ films via grain boundary diffusion of Mn

Post-deposition rapid thermal annealing (RTA) was performed on the Cr-less Co-20 at%Pt alloy with a Mn diffusion layer on top. A Ku value of about 8/spl times/10/sup 6/ erg/cm/sup 3/ was obtained for the as-deposited film and it decreased only up to about 10% after annealing. The high intergranular exchange coupling of the as-deposited CoPt film was suppressed by RTA and the coercivity increased dramatically from about 2200 to 6000 Oe. The energy-filtered TEM plane-view images showed depletion of Co and aggregation of Mn at the CoPt grain boundaries. This is a direct evidence supporting preferential diffusion of materials from adjacent layers into magnetic grain boundaries.