MICROSTRUCTURE AND INTERGRANULAR COUPLING IN COCRTA THIN-FILM MEDIA FABRICATED USING AN ULTRACLEAN SPUTTERING PROCESS

The microstructure and intergranular coupling in Co85.5Cr10.5Ta4 and C o78Cr17Ta5 media fabricated using an ultraclean (UC) process are discu ssed in relation to the thickness of the Cr underlayer. The purificati on of the deposition atmosphere by applying the UC process is found to be most effective for deriving high H-c in both media. In UC-Co78Cr17 Ta5, a high H-c of about 2.1 kOe remains even at a Cr thickness of 2.5 nm, With the UC process the Cr segregated grain boundary structure is enhanced even in media with thin Cr underlayers, which causes a remar kably low intergranular exchange coupling, The increase in the strengt h of intergranular magnetostatic coupling due to the grain size reduct ion strongly influences the reduction in H-c/H-k(grain) with decreasin g Cr thickness, In UC-Co78Cr17Ta5 with extremely thin Cr underlayers, the sufficiently segregated grain boundary structure and the intrinsic ally low intergranular magnetostatic coupling are responsible for the realization of very high H-c/H-k(grain).