Dual-layer patterned media “ledge” design for ultrahigh density magnetic recording

Patterned media elements comprising coupled magnetically hard and soft sections of different horizontal size, referred to as ledge elements, are characterized by several unique properties. These elements allow for remarkably reduced reversal fields, which are an order of magnitude below the Stoner-Wohlfarth limit. They also allow for precessional reversal to occur for practical field rise times $(100–200ps)$⁠, which are two orders of magnitude larger than those in the case of homogeneous elements $(∼2ps)$⁠. These attractive properties are obtained even for elements of small height $(4–8nm)$⁠. Patterned media implementing such ledge elements can allow for recording densities above $10Tbit∕in2$⁠.