Performance evaluation of different pole geometries in thin film heads

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 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