Patent ID: 7435489

Claim:
A magnetic recording medium comprising: an exchange layer structure; and a magnetic layer provided on the exchange layer structure, said exchange layer structure comprising a ferromagnetic layer and a nonmagnetic coupling layer provided on the ferromagnetic layer, said ferromagnetic layer and said magnetic layer being exchange-coupled and having mutually antiparallel magnetizations, said ferromagnetic layer and said magnetic layer satisfying a relationship Hc 1 ′≧Hc 2 ′, where Hc 1 ′ denotes a dynamic coercivity of the ferromagnetic layer and Hc 2 ′ denotes a dynamic coercivity of the magnetic layer, each of the dynamic coercivities Hc 1 ′ and Hc 2 ′ referring to a coercivity for a case where a time required to switch a direction of an external magnetic field is on the order of sub-nano second to approximately one nano-second order, said ferromagnetic layer and said magnetic layer satisfying a relationship Hc 1 <Hc 2 , where Hc 1 denotes a static coercivity of the ferromagnetic layer and Hc 2 denotes a static coercivity of the magnetic layer, each of the static coercivities Hc 1 and Hc 2 referring to a coercivity for a case where a time required to switch a direction of an external magnetic field is on the order of seconds or greater, each of the ferromagnetic layer and the magnetic layer is made of a material selected from a group consisting of CoCrPt and CoCrPt-M alloy, where M is an element or alloy thereof selected from a group consisting of B, Mo, Nb, Ta, W and Cu, and a Pt content of the magnetic layer in atomic % is less than a Pt content of the ferromagnetic layer in atomic %, and said ferromagnetic layer has a thickness in a range of 1 nm to 10 nm.