Effects of grain size and intergranular coupling on recording characteristics in CoCrTa media

The effects of grain size on intergranular magnetostatic coupling and on recording property are discussed for the Co85.5Cr10.5Ta4 and Co78Cr17Ta5 thin film media fabricated under the ultra clean sputtering process (UC-process). S/N-m increases not only with the increment in H-c/H-k(grain) but also with the decrement in the grain diameter in both CoCrTa media. In the media with high H-c/H-k(grain) value more than 0.35, S/N-m drastically increases with decrease in the grain diameter, which corresponds to the decrease in the dispersion of magnetic field strength from recorded bits. To maintain high H-c/H-k(grain) value more than 0.35 even in the media with small grain size below 10 nm, the selection of alloy composition which gives a small 4 pi M(s)/H-k(grain) value of less than 1.0 is required.