Experimental write margin analysis of bit patterned media

Write margin analysis of the bit patterned media (BPM) was experimentally carried out using a static tester. Sample BPM were fabricated from hard/soft-stacked (exchange-coupled composite; ECC) base media with a Pt/Co multilayer hard layer and a Co soft layer. Write margins of 60-nm-dot (140 nm period) and 40-nm-dot (100 nm period) media were confirmed to be 80 nm and 50 nm, respectively. An analysis of the margin loss factor found a large residual margin loss. The loss factors of 60-nm-dot and 40-nm-dot media were 57 nm and 44 nm, respectively, and these values almost correspond to the dot diameter. The residual margin loss was identified as due to the formation of a multi-domain structure within some dots under certain recording conditions.