Proposal of Granular-Type Cap Layer with High- $K_{u}$ CoPt Grains and Ferromagnetic Oxide Grain Boundaries for Full Granular Media

Investigation of magnetic properties and microstructure for the stacked media with Co
₈₀
Pt
₂₀
-30 vol% rare earth (RE) oxide (RE oxide: Gd
₂
O
₃
, Nd
₂
O
₃
, and Sm
₂
O
₃
) cap layers (CLs) deposited on a Co
₈₀
Pt
₂₀
-30 vol% B
₂
O
₃
granular recording layer (GRL) was conducted. It was found that the employment of a granular-type CL with ferromagnetic oxide is effective to control intergranular exchange coupling of the magnetic grains in CoPt-B
₂
O
₃
GRL while maintaining the granular structure of the CL. In this full granular media, continuous structure of columnar magnetic grains and grain boundaries from the GRL up to the CL can be observed. When a typical ferromagnetic oxide CL, such as CoPt-Gd
₂
O
₃
(9 nm), is deposited on CoPt-B
₂
O
₃
GRL (16 nm), the nucleation field is increased from 0.7 to 1.1 kOe, and the saturation field is reduced from 21.5 to 16 kOe which suggest that CoPt-RE oxide is promising for a CL.