Comparison of ring head and SPT head write fields

The coefficients of Fan ring head and single-pole-type (SPT) head of various gap widths/pole thicknesses were evaluated and the head field distribution for various configurations and flying heights were calculated. For easy visualization in comparison with Karlquist field the head fields are expressed in reduced units as
H\min{xy}\max{F} = H\min{xy}\max{K}+ H\min{xy}\max{C}
where F, K, and C stands for Fan, Karlquist, and correction terms, respectively. The results show the following. 1) The ring head coefficients are independent of gap width while the SPT head coefficients vary with the ratios of pole thickness to flying heights. The latter coefficients approach that of the ring head in the limit if it is properly redefined, indicating similarity and dissimilarity between the two head fields. 2) In the gap region the write field of a ring
head F\min{Rx}\max{F}
bends downward in comparison with Karlquist field, reaching approximately 0.82 at very low flying heights. 3) The x-component ring head field
H\min{Rx}\max{F}
differs considerably from the y-component SPT head field
H\min{py}\max{F}
when measured along the direction of media motion. The two fields behave similarly to each other only if each is measured along the direction of its own image plane.