Microstructure and magnetic properties of perpendicular media with reduced grain size

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 Ru1 layer, on top of which a granular Ru2+SiO2 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 +SiO2 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 Hc of the media is 2.7 kOe, while Hc 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 Hc and remanent magnetization Mr and increasing Hn−Hc values of the perpendicular MH loops. © 2009 American Institute of Physics. DOI: 10.1063/1.3070586