Wavelength response of ring-type head with arbitrary gap depth

In 1953 Westmijze found analytic solutions for the fields and wavelength responses of ring-type-head models with zero and infinite gap depths and demonstrated that the wavelength responses for these two extreme cases are substantially different. A model two-dimensional electromagnet that is equivalent to a more general ring-type-head model that takes into consideration a final gap-depth value is considered. It is shown that the Westmijze head models are actually two specific cases of this more general model. Using the theory of complex analytic functions, the gap between the two Westmijze models is bridged and an analytic solution for the wavelength response of a ring-type head with an arbitrary gap depth is derived. Graphs of the responses calculated for several gap depths are presented. These graphs illustrate that the gap depth has no practical effect on wavelength response as long as the ratio of pole thickness to gap size exceeds 0.5. However, further decrease of this ratio causes considerable changes in wavelength responses     

Theoretical Comparison of readback harmonic responses for longitudinal recording and perpendicular recording with probe head over a medium with permeable underlayer

In this work we compare the theoretical readback harmonic responses of longitudinal and perpendicular recording with ideal two-dimensional heads which have infinite permeable cores. The comparison provides a clear picture of the difference between the readback performance of longitudinal and perpendicular recording.     

Comparison of sensitivity functions for ideal probe and ring-type heads

Analytical models of ideal infinitesimally thin probe-type heads have been presented and compared with a model of an ideal ring-type head. It is shown that with respect to readback resolution the characteristics of probe models are inferior to those of the ring model. It is also shown that resolution of the probe model is reduced further if media with a soft magnetic underlayer is used.     

Characteristics of ideal probe heads with ideal windings in the presence of a permeable media underlayer

An analytical expression has been derived for the field of a two-dimensional infinitesimally thin probe head with the winding located at a finite distance from the probe tip. The results of the calculations presented illustrate the effect of the location of the winding on the fields of head models and their aperture functions.     

Theory of playback process with soft magnetic underlayer

Based on the Tsuboi-Fushida-Wallace spacing loss law, reciprocity principle, and the principle of an image plane, a two-dimensional, head independent theory of the playback process has been developed for perpendicular magnetic recording (PMR) media with a soft magnetic underlayer (SMUL). An assumption that the reversible magnetic permeability of the recording media is equal to one gives results in a simple form. The article, while not addressing the effect of underlayer on write performances, demonstrates complications caused by the presence of the underlayer during readback.