Recording performance of double-layered perpendicular recording media with an antiferromagnetic layer

For a double-layered perpendicular media having an antiferromagnetic layer, it has been reported that increasing the exchange bias field H/sub ex/ is effective to reduce spike noise generated from the domain walls of the soft magnetic underlayer (SUL). In this study, a high exchange-coupling energy J/sub ex/ of 0.345 erg/cm/sup 2/ was obtained by using the combination of a NiFeB underlayer and a CoFeNiB enhancement layer. By investigating the effects of H/sub ex/ on the recording performance, it was revealed that increasing H/sub ex/ caused the writability of a head to deteriorate. However, reducing the nonmagnetic interlayer thickness, which reduces the magnetic spacing between the head and the SUL, could minimize the deterioration in writability. In addition, when the writability was unaffected by H/sub ex/, the signal-to-media-noise ratio was improved by the effect of SUL domain noise reduction.