Nonlinear finite element calculations show that the soft underlayer thickness in perpendicular media can be greatly reduced without significant loss of effective switching field strength by using a shielded pole writer in place of the more conventional monopole geometry. In addition, use of a thin soft underlayer (SUL) with a shielded pole writer with a thin SUL results in a higher gradient and a narrower magnetic write width. These results have been qualitatively confirmed experimentally.

Measurement of the harmonics of low-frequency all-ones patterns and the shield-to-shield read gap are used here to reconstruct the spacing, the isolated transition shape, and the width parameter for longitudinal recording. For perpendicular, the media thickness parameters and data at two spacings are needed to accurately determine the spacing and width parameter.The 90% to +90% transition shapes fits well to a tanh( ) shape for longitudinal and perpendicular recording.

To achieve higher areal density, inductive thin film recording heads require smaller track pitch. Pole trimming of conventional heads where P1 width is made equal to the P2 width is suggested in literature as a method for increasing the track density. A patented design called the bevel head [l]where pole P1 of the conventional head is beveled to have the same width as P2 width at the gap, is shown to have equivalent offtrack performance as the pole trimmed heads. The bevel heads require a simpler process to manufacture compared to the pole trimmed heads. Three dimensional field maps are computed for conventional heads, pole trimmed heads and for the beveled heads at different values of write currents. Using these field maps, a simulation of the recording process is done to compute the erase width, write width, read width and isolated pulse response. Both pole trimmed heads and the bevel heads show improvement over the conventional heads in ,.accomplishing a narrower erase width. An offtrack capability model is developed to fit the experimental 747 curve based on the microtrack profile, erase width and a SNR value. Using this model, track density is calculated for all the three heads. Pole trimmed heads and bevel heads show a similar improvement over conventional heads in accomplishing higher track density.

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