Observations on Perpendicular Magnetic Recordings of High Recording Densities on Co-Cr Films by the Colloid-SEM Method

Perpendicular magnetic recordings of 5 to 100 kBPI densities on evaporated Co-24 wt%Cr films of 2200 Å in thickness have been observed by the colloid-SEM method and by the conventional magnetic powder pattern technique. The latter technique, using an optical microscope, gives satisfactory results for recording densities of 5 and 10 kBPI. For high recording densities of 50 and 100 kBPI, clear recorded patterns have been successfully obtained by the colloid-SEM method where dried powder patterns are made under external magnetic fields of 200 to 300 Oe applied vertically to the film planes. It is shown that a better recording can be determined from the obtained patterns, even in high-density recordings. Some discussions are given regarding the relation between the single-domain behaviour of columnar grains in the films and obtained recorded patterns.