Thin film and ferrite head recording on metallic coated disks

Abstract

Linear superposition based on simple theory suggests that the linear bit density increase for the thin film (or finite pole width) head is about 25 percent over that of conventional ferrite (or Karlquist) head technology. Realistic dynamic simulations conclude that although the thin film head is excellent for writing, it is a poor read head due to a lack of low frequency response. This creates readback signal baseline wander, and sensitivity to amplitude modulation and peakshift. The commonly observed narrow isolated read pulse from a thin film head, therefore, is only one necessary condition to achieve high bit density, however, it is not a sufficient condition. Interestingly, to achieve high density without performance degradation, a novel combination would be a narrow pole width geometry for WRITE and a wide pole width for READ. Magnetization transitions and readback signals (before and after sub-optimal spectral equalization) of a Quadruplet data pattern using thin film and ferrite heads on a calibrated Ni-Co metallic coated disk were compared and investigated in depth.