Magnetic and thermomagnetic analysis of 4 megabyte barium ferrite flexible disks

The four megabyte flexible disks utilize unoriented coatings of barium ferrite particles. Comparing the disks from ten different manufacturers, the author observed considerable differences in soft error rates. A detailed magnetic and thermomagnetic analysis revealed significant differences between the various disks, but not sufficient to explain the differences in error statistics. It is concluded that the error differences originate primarily from the differences in high-frequency (short-wavelength) modulation caused by surface roughness variations