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To achieve ever-increasing areal density, magnetic recording heads are required to operate at ever-decreasing trackwidths. The shield width of a magnetoresistive head is an important factor in the off-track performance of the head. Reducing the shield width at the ABS will reduce the off-track inductive response (inductive pickup by MR device acting as a one-turn inductive head with trackwidth equal to the shield width) at the cost of increasing the off-track magnetoresistive response. In this study, the effect of the shield width at the ABS on the off-track inductive and off-track M R noise was examined.a shield-to-shield spacing of 0.31 p, bottom and shared shield thicknesses of 2.0 pm and 3.5 pm, respectively, a smpe height of 1.8 pn, and a flying height of 63 nm. The disk had an M& of 1.0 memu/cm2, a of 2200 Oe, and a linear velocity of 620 ips. The low frequency was 7.0 MHz. The cross-track geometry studied is shown in Figure 1.Using a finite-difference model and common assumptions about the potential at the ABS [ 11, the head potential is modeled for various shield widths. A sample potential profile is shown in Figure 2 for a shield width of 20 pm. 3D reciprocity was used to calculate the response to a microtrack as a function of off-track position. This will be discussed. In the model, the shield width, w, was varied from 2.6 pm (shields flush to the MR element) to 150 pm.Focused-Ion-Beam etching was used to fabricate devices with shield widths varying from 6 pm to 150 pm. The depth of the etched region was 1 pm. To measure and visualize off-track pickup in an intuitive way, a center track was written at the low frequency (LE). 20 tracks were written toward the ID at a frequency of (LF-n*50 IcHz), where n is the number of tracks from the center track, and 20 tracks were written in the OD direction at a frequency of (LF+n*50 IcHz). The track pitch was 4.2 lun. The head was placed on the center track and the signal was analyzed by a spectrum analyzer. The magnitude of the signal at a given frequency (LF+n*50kHz) measures the amount of off-track pickup from the nth track. Figure 3 and 4 show the inductive response (bias current off) and the total response, MR plus inductive, (bias current on) for a sample shield width of 10 p Figure 5 and 6 show the inductive response and the total response, M R plus inductive, for a sample shield width of 150 pm, The head with the 10 pm shield width clearly shows less off-track inductive signal from the outlying tracks as well as a significant decrease in the noise floor in that region. An increase in the off-track MR response (total response minus inductive response) is not seen at this shield width. The left-right asymmetry in the total response is due to anisotropic flux propagation in the MR element.The response for all shield widths and the optimum shield width at the ABS, based on minimizing the two noise sources considered here, will be discussed.The head studied was an MR head with a read trackwidth of 2.6 References[I]

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