Head/Media Integration Challenge Toward 1 ${\hbox{Tb/in}}^{2}$ Perpendicular Recording

Abstract

We investigated medium noise using spinstand testing and calculation from the view point of head/media integration for 1 Tb/in 2, focusing on two kinds of noise sources: transition noise in the track center and track edge noise. A quantitative relationship between transition noise and magnetic cluster size of media was clarified. This relationship indicates that the transition noise can be reduced by reducing the magnetic cluster. In the track edge noise, there are two noise sources: edge line fluctuation and increase in transition length at the edges. The edge line fluctuation noise degrades low density SNR. We show that a high cross-track field gradient of writer and small magnetic cluster of media are effective to reduce the edge line fluctuation. The increase in transition length at the edges degrades high linear density SNR. The transition length at the edges increases as transition curvature increases. Both increase in transition length at the edges and large transition curvature make the magnetic write width narrow and erase band width wide. Large track edge noise was observed when the transition curvature was large. Therefore reducing the transition curvature is an effective way to reduce track edge noise. In the micromagnetic calculation for 1 Tb/in2 , high 2 T-SNR of 13.7 dB (1 T: 2200 kfci) at magnetic write width of 54 nm was obtained from a combination of graded Hk media with small magnetic cluster and wraparound shielded writer with high cross-track field gradient and small transition curvature.