Perpendicular magnetic recording exchange-spring type medium with a lateral coupling layer for increasing intergranular exchange coupling in the lower magnetic layer

Abstract

A perpendicular magnetic recording system and medium has a multilayered recording layer that includes an exchange-spring structure and a ferromagnetic lateral coupling layer (LCL). The exchange-spring structure is made up of two ferromagnetically exchange-coupled magnetic layers (MAGand MAG), each with perpendicular magnetic anisotropy. MAGand MAGmay have a coupling layer (CL) located between them that permits ferromagnetic exchange coupling of MAGwith MAG. The LCL is located either above or below MAGand in direct contact with MAGand mediates an effective intergranular exchange coupling in MAG. The ferromagnetic alloy in the LCL has significantly greater intergranular exchange coupling than the ferromagnetic alloy in MAG, which typically will include segregants such as oxides. The LCL is preferably free of oxides or other non-metallic segregants, which would tend to reduce intergranular exchange coupling in the LCL. Because the LCL grain boundaries overlay the boundaries of the generally segregated and decoupled grains of MAG, and the LCL and MAGgrains are strongly coupled perpendicularly, the LCL introduces an effective intergranular exchange coupling in the MAG