Cross-sectional structures and depth profiles in bias sputtered GdCo films

Structures and compositions of sputtered GdCo films were carefully investigated using a carbon-replica technique and Auger electron spectroscopy. In zero-bias sputtered films, the columns are clearly observed to develop perpendicular to the substrate, and they become fine with increasing Gd content up to near the compensation composition from pure Co film. For negative-bias sputtered GdCo films having near compensation composition, the film structures become fine with increasing negative bias up to 200 V. The observed increment of perpendicular anisotropy in this negative bias region was explained by the structural change of the columns (shape anisotropy and stress induced anisotropy). Above 200 V negative bias, the column structures are damaged partially by Ar-ion-bombardment, and then the anisotropy decreases due to the damage of columns. The change in the saturation magnetization due to negative bias was interpreted by the change in the film composition; Gd-content and oxygen.