Electron microscopy studies of the surfaces of magnetic recording media

A technique has been developed for replicating the surfaces of magnetic recording media. The media used included new magnetic tape, used magnetic tape, and "Hypalon" disks; this latter material is used in recording belts. Magnifications ranged from 10,000 × to 80,000 × direct magnification, and up to 240,000 × by photographic enlargement. The electron micrographs thus obtained show a very much smaller unit crystal size for γ-ferric oxide than previously supposed. There is also an apparent relationship between the magnetic properties and the dispersion and unit particle size of the iron oxide particles on the tape surface.