They used a thin film of a commercially available nickel-iron magnetic alloy called Permalloy for the disk.    From Wordnik.com.  [PhysOrg.com - latest science and technology news stories] Reference

He said "Patchwork Permalloy" got a lot of attention with its resemblance to wrapping paper, allowing it to earn spaces in both the December section and on the cover, which he said is usually reserved for the best composition.    From Wordnik.com.  [news | TL | http://www.tuscaloosanews.com] Reference

A researcher for Alabama's Center for Materials for Information Technology, Mankey was previously chair of the Magnetic Interface and Nanostructures Division of the AVS Science and Technology Society, where he entered "Patchwork Permalloy" in AVS's Art Zone contest.    From Wordnik.com.  [news | TL | http://www.tuscaloosanews.com] Reference