Volume Ratio Effect of Dual Oxides With a Different Melting Point on Microstructure of High Ku Co80Pt20 Granular Media

A systematic investigation on magnetic properties and microstructure of Co
₈₀
Pt
₂₀
-B
₂
O
₃
mixed with a high-melting-point oxide of various contents was conducted. It was found that the dual oxides granular media with moderate magnetic properties could be realized by changing the oxide fraction, which could not be realized by only utilizing a single oxide. The reduction of magnetic grain size could be obtained by employing a second oxide with high melting point due to the suppression of lateral magnetic grain growth by high-melting-point oxide at the initial growth region. The control of volume fraction of the high melting point was very essential to obtain small magnetic grains with columnar growth. To obtain a granular medium with small average grain size and narrow distribution, the application of an underlayer with smaller grain size would be needed. A significant reduction of grain size from 5.6 to 4.7 nm in a typical dual oxides granular medium could be observed when 30 vol% B
₂
O
₃
was partially replaced by 15 vol% Cr
₂
O
₃
.