Patterning of granular magnetic media with a focused ion beam to produce single-domain islands at > 140 Gbit/in²

We have used a focused ion beam to directly pattern thin- film granular perpendicular Co70Cr18Pt12 media. By cutting trenches ∼6 nm deep in the ∼20 nm media, we have produced square arrays of magnetically isolated islands with periods in the range 65-500 nm. At periods below ∼130 nm we observe only single magnetic domains, which exhibit a rough "checker-board" pattern of upon ac demagnetization. We have patterned at densities of over 140 Gbit/in2.