Microstructure and magnetic properties of perpendicular media with reduced grain size

摘要

A new approach to control the grain size of Co alloy oxide perpendicular media by means of Ar-ion etching is presented. Ar plasma was applied to the surface of a continuous Rul layer, on top of which a granular Ru2 + SiO_2 layer was subsequently deposited. It was found that etching time and high Ar-ion energy have a significant effect on the surface roughness of the seedlayer, which in turn have a great effect on microstructure and magnetic properties of the media. A granular Ru2 + SiO_2 layer with mean grain size of 3.9 ±0.7 nm was obtained, and its oxide boundary thickness decreased with the decreasing Ru grain size. As a result, the mean grain size of the magnetic layer was greatly reduced to 5.3 ±0.8 nm from 7.6 ±1.3 nm of a controlled sample without Ar-ion etching. The coercivity (H_c) of the media is 2.7 kOe, while H_c of the controlled sample is 4.8 kOe. The small CoPt grain size, the possible oxidization of metal grains, and the resultant increasing c-axis dispersion of the magnetic layer can explain the decreasing H_c and remanent magnetization (M_r) and increasing (H_n-H_c) values of the perpendicular MH loops.