Reduction of Intergranular Exchange Coupling for CoPt–B2O3 Granular Media by Employing a RuCoCr-Oxide Buffer Layer With Oxide of Various Melting Points

Investigation of magnetic properties and microstructure for the Co
₈₀
Pt
_20-30
vol% B
₂
O
₃
granular medium deposited on Ru
₅₀
Co
₂₅
Cr
_25-30
vol% oxide buffer layer (BL) with oxide of various melting points was conducted. It was found that by employing a BL, coercivity of the granular medium is enhanced due to the promotion of intergranular exchange decoupling. Thickness of the BL to obtain the maximum coercivity can be reduced when oxides with high melting point is utilized. Significant reduction of grain diameter (GD) of the granular medium is obtained when a thick BL with high-melting point oxide is applied. For a typical Ru
₅₀
Co
₂₅
Cr
_25-30
vol% TiO
₂
BL of 2 nm, a granular medium with high coercivity, anisotropy field, and small magnetic GD of 9.4, 19.5 kOe, and 5.6 nm, respectively, can be achieved.