Patent ID: 7125616

Claim:
A magnetic recording disk comprising: a substrate; and an antiferromagnetically-coupled (AFC) magnetic recording layer on the substrate and having two remanent magnetic states in the absence of an applied magnetic field, the AFC recording layer comprising (a) a first lower ferromagnetic layer having a remanent magnetization Mr, a thickness t and a remanent-magnetization-thickness product Mrt; (b) a first antiferromagnetically coupling layer on the first lower ferromagnetic layer; (c) a second lower ferromagnetic layer on the first antiferromagnetically coupling layer and having an Mrt less than the Mrt of the first lower ferromagnetic layer; (d) a second antiferromagnetically coupling layer on the second lower ferromagnetic layer; (e) a third lower ferromagnetic layer on the second antiferromagnetically coupling layer and having an Mrt greater than the Mrt of the second lower ferromagnetic layer; (f) a third antiferromagnetically coupling layer on the third lower ferromagnetic layer; and (g) an upper ferromagnetic layer on the third antiferromagnetically coupling layer and having an Mrt greater than the sum of the Mrt values of the first and third lower ferromagnetic layers; and wherein the magnetization directions of the upper ferromagnetic layer and the third ferromagnetic layer are substantially antiparallel in each remanent state, the magnetization directions of the second lower ferromagnetic layer and the first ferromagnetic layer are substantially antiparallel in each remanent state, and the magnetization direction of the upper ferromagnetic layer in one remanent state is substantially antiparallel to its magnetization direction in the other remanent state.