Co-X （X=Cr, Mo, W） magnetic thin films were prepared by using DC magnetron sputtering, and their structures were examined by using X-ray diffraction （XRD）. The amorphous forming ability （AFA） of the three alloy systems was discussed based on thermodynamic calculation and experiments. The results show that the Co-Mo thin films exhibit the largest AFA among them, and the Co-W thin films are conditiondependent amorphous while the Co-Cr thin films are hard to be amorphous, which is consistent with the thermodynamic calculation. The difference in AFA for the alloys of these three systems is finally ascribed to three main factors： differences in electronegativity, electron density and atomic size between Co and X elements.
Gaowu QIN Na XIAO Bo YANG Yuping REN Wenli PEI Xiang ZHAO
The microstructure and magnetic properties of Co/Cr bilayer films were examined before and after postdeposition annealing by using transmission electron microscopy （TEM）, X-ray diffraction （XRD） technique and vibrating sample magnetometer （VSM）. A model of grain boundary （GB） Cr-rich phase growth involving GB diffusion derived from the Cr underlayer was proposed to elucidate the kinetics of the paramagnetic Cr-rich phase growth along Co GBs within the Co layer. The correlation of the GB Cr-rich phase formation with the magnetic Co grain isolation and accordingly, improvement of magnetic properties was experimentally investigated and discussed in detail. Our analysis results are well consistent with previous micromagnetic simulations on the improvement of magnetic properties by the magnetic grain isolation. The results provide some insights into the processing-structure-property relationships of the Co/Cr bilayer films, and thus suggest that the magnetic grain isolation be feasible not only in longitudinal recording media, but also be effective in tuning the exchange coupling of magnetic grains in perpendicular recording media via the GB diffusion from underlayer and/or overlayer.
A series of hexagonal close-packed （HCP） Co-W thin films were deposited by sputtering on surface oxidized silicon substrates at 300 ℃. A linear dependency of saturation magnetization （Ms） on W content was found up to about 9 at. pct W, and then it underwent an increased Ms vs. W content curve as compared to the initial linear dependency. The thermal magnetization technique was used to confirm that the ino creased Ms behaviour is correlated to the phase separation of the Co-W thin films. The phase separation behaviour was also found to be dependent on W content and the reason was discussed in detail. Finally an interesting composition range was suggested to be about 13 at. pct-17 at. pct W for the Co-W thin films, in which they exhibit much higher magnetic anisotropy energy than Co-Cr thin films and improved phase separation.
Bo YANGGaowu QINWeili PEIYuping RENNa XIAOXiang ZHAOKatsunari OIKAWA
