EFFECT OF MICROSTRUCTURE ON MEDIA NOISE OF COCRTA THIN-FILM MEDIA FABRICATED UNDER ULTRA CLEAN SPUTTERING PROCESS

Ultra clean sputtering process (UC-process) was introduced In the fabr ication of Co85.5Cr10.5Ta4/Cr thin film media Magnetic properties, mic rostructure and their effect on media noise are discussed against the thickness of Cr underlayer. By applying the UC-process, coercive force H-c shows high values of about 2.3 kOe isotropically until 10 nm in C r thickness. High H-c of about 1.5 kOe remains at even 2.5 nm. UC-proc ess is found to enable the enhancement of the formation of Cr segregat ed grain boundary structure, which reduces intergranular exchange coup ling even in the media with 2.5 nm in Cr thickness. The ratio of readb ack signal to media noise S/Nm gradually increases with decreasing Cr thickness, and shows the highest value at 2.5 similar to 5 nm. In the media with sufficiently separated grains by segregated grain boundarie s, the reduction of the grain size with decreasing Cr thickness is fou nd to be most effective for the improvement of S/Nm.