Scanning force microscopy and magnetic force microscopy imaging of the surface structure of a large capacity floppy disk

Simultaneous scanning force microscopy (SFM) and magnetic force microscopy (MFM) observation of the surface topography and magnetic bit patterns (track width of 9 μm and shortest bit-length of 0.75 μm) at the same small surface region of a large capacity floppy disk (100 Mbyte on a 3.5-inch disk) is shown. It is revealed that irregular distributions of hexagonal platelet Ba-ferrite fine magnetic particles (50 nm diameter and 20 nm thickness) and abrasive aluminum particles on the surface are major causes of nonuniformity in the magnetic force gradient map of the MFM image. A brief description of the disk drive and some characteristic readout data are also given