Corrosion improvement and magnetic properties of CoCr with small Gd additions

Sputtered films of composition 79 at.%-Co 21% Cr have been prepared with Gd substitutions. For small Gd concentrations, crystallinity, and perpendicular anisotropy are maintained. For higher concentrations (4% Gd), amorphous materials are obtained. Crystalline materials show a lack of, or diminished phased segregation compared to unsubstituted CoCr. This is manifested in the magnitudes of saturation moment and Curie temperature which are comparable to the values of the target materials. Phase-segregated CoCr films, by comparison, show relatively high values. Corrosion resistance of CoCrGd materials as measured by anodic polarization curves is strongly improved over that for phase-segregated materials. This appears to have to do with the more homogeneous microstructure of the materials. Intermediate segregations can be obtained with smaller Gd substitutions. These films combine suitable parameters for magnetic recording with strongly improved corrosion resistance relative to the unsubstituted materials.