A 5 megabyte flexible disk

The data capacity of a double-sided, 8" diameter flexible disk has been increased from 1.26 megabytes without any substantial enhancement of the magnetic properties. Iron oxide particles of acicularity
\sim5:1
and a coercivity of 300 Oe were used; however, the coating thickness was reduced from 100μ" (2.5μm) to 40μ" (1.0μm) to permit a linear density of 10,700 flux changes per inch on the innermost track to be achieved with a resolution (2F/1F amplitude) of 0.72 and a peak shift <4%. The design constraints are described and the problems of formulation, processing and testing are discussed.