Microstructure of a Co-CoO obliquely evaporated magnetic tape

Microstructure of a Co-CoO obliquely evaporated tape for magnetic recording was studied by transmission electron microscopy with an energy-dispersive x-ray spectrometer and an energy filter. Columnar structure of Co-rich region spanning through the film thickness was observed. The diameters of the columns increased from 20 nm at the bottom to 40 nm at the top of the film. Within a column, several chains of Co crystallites lying along the column axis were observed. Individual Co crystallite constituting a chain had a diameter between 5 and 10 nm. In the lower part of the column, several chains assembled to form a bundle. In the upper part, the Co chains were separated by CoO crystallites in the enlarged diameter of the column. A typical diameter of a Co crystallite was smaller in the upper part of the film than that observed in the lower part. CoO crystallites were found to be densely packed between Co-rich columns whereas previous studies had interpreted the regions between the Co columns to be voided or less dense.