A perpendicular magnetic recording medium has an “exchange-spring” type magnetic
recording layer (RL) formed of two ferromagnetic
layers with substantially similar
anisotropy fields that are ferromagnetically exchange-coupled by a nonmagnetic or weakly ferromagnetic
coupling layer. Because the write head produces a larger
magnetic field and larger field gradient at the upper portion of the RL, while the
field strength decreases further inside the RL, the upper ferromagnetic layer can have a high
anisotropy field. The
high field and field gradient near the top of the RL, where the upper ferromagnetic layer is located, reverses the
magnetization of the upper ferromagnetic layer, which then assists in the
magnetization reversal of the lower ferromagnetic layer. Because both ferromagnetic
layers in this exchange-spring type RL have a high
anisotropy field, the
thermal stability of the medium is not compromised. The medium shows improved writability, i.e., a low switching field, as well as lower intrinsic media
noise, over a medium with a conventional single-layer RL.