Recording performance of CoCrPtO perpendicular media with single-domain hard magnet-biased soft magnetic underlayers

Single-domain hard magnet-biased (HB) soft magnetic underlayers (SUL) with synthetic antiferromagnetically (SAF) coupled structure were successfully produced. Here, we describe the effect of HB SAF SUL on recording performance in a simple structure of Co86CrTa(40)∕Ru∕CoTaZr(t)∕interlayer(15)∕CoCrPtO(15nm). Radial anisotropy orientation of as-deposited CoTaZr films was induced at thickness ⩾60nm. As CoTaZr thickness increased from 60to195nm, media write-ability was significantly improved while magnetic properties of the CoCrPtO layer were slightly changed. Normalized media noise data are consistent with magnetic domain observation: Kerr images exhibited single magnetic domain, but magnetic force microscopy images detected strong magnetic ripple structure at 60nm. Less magnetic ripple was observed with increasing CoTaZr thickness. The magnetic ripples on CoTaZr, caused by exchange coupling with CoCrTa, clearly contributed to dc-erase noise. Media noise and signal-to-noise SNRme on 155nm thick CoTaZr were co...