I. Introduction
Perpendicular recording technology has advanced significantly with areal density approaching 300 Gb/in2 in commercially available products today. In order to sustain high areal density with adequate thermal stability, advanced media structures such as exchange spring (ES) or exchange coupled composite (ECC) media comprising hard and soft layers in the grain [1], [2] or coupled granular/continuous (CGC) media [3] have been proposed to improve writeability of high anisotropy grains. These approaches are designed to reduce the switching field of the high grains that are exchange-coupled to the soft layer which starts switching at a lower applied field than that of the hard layer while adequate thermal stability is maintained. Several research groups attempted to fabricate the media structure to explore the proposed advantages of ECC media as well as CGC media [4], [5]. Although the enhanced media writeability was successfully demonstrated, the predicted noise reduction necessary for high density recording was insignificant. The key challenge to enhance the media signal-to-noise ratio (SNR) in the composite media is to fabricate the reduced grain in the hard layer with higher , prior to stacking the soft layer onto the hard layer.