Patent ID: 7081309

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