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Return field-induced partial erasure (RFPE) in trailing-edge shielded perpendicular writers has been studied, both by modeling and by experiments. For a given head-media combination, the return field underneath the trailing shield increases with increasing write current. Once exceeding a certain threshold, it will cause partial erasure of the bits that have just been written by the main pole. Recording performance, such as reverse overwrite, spectral signal-to-noise ratio, and bit-error rate are all found degraded at high write currents, due to RFPE. Design optimization of both head and media together is needed, in order to maximize the advantage of a trailing-edge shielded pole head and minimize the impact of RFPE. Index Terms--Partial erasure, perpendicular recording, return field, shielded pole head.

We studied the remanent field from perpendicular writer pole tips by micromagnetic modeling. The pole tip remanence has two causes: 1) the residual flux from the yoke due to undesirable material properties and/or yoke design and 2) the geometry of the pole tip. An optimal yoke design for low remanence includes a wide and short yoke with relatively shallow yoke flare angle around 30[degrees] that favors transverse major domains. Horizontal anisotropy in the yoke and the pole tip also helps suppress the vertical magnetization, mainly in the yoke, which yields less residual flux into the pole tip, hence lower remanence. The remanent field is also a strong function of the throat height, i.e., the pole tip length, due to the shape anisotropy effect. Micromagnetic modeling shows that multilayer lamination, both in the yoke and in the pole tip, is an effective way to achieve low remanence. It also eliminates the sensitivity of remanence to the throat height. To improve the robustness of the remanence against the stray field, an antiferromagnetic coupling (AFC) between the lamination layers may also be necessary. Our results apply to both single pole heads and shielded pole heads. Index Terms--Antiferromagnetic coupling (AFC), head lamination, micromagnetic modeling, perpendicular recording, pole tip remanence, remanent erasure, shielded pole head, single pole head.

We present a micromagnetic modeling on the readback process of perpendicular recording with soft underlayer (SUL). The effect of the SUL on readback has been investigated. The SUL imaging effect enhances the readback signal amplitude differently for high density and low density, making the rolloff of the readback signal faster with the linear density and, thus, deteriorating the readback performance by lowering the maximum achievable linear density. Most approaches for increasing the density limit via making the SUL imaging less effective are accompanied by the tradeoff of the write field loss. Reducing the head-medium spacing and the reader gap with an optimized spin valve reader stripe height are essential for maximizing the linear density limits imposed by the rolloff of the readback. Index Terms--Linear density limit, micromagnetic modeling, perpendicular recording, readback, soft underlayer.

Using a dynamic micromagnetic write model, we have studied the spectral signal-to-noise ratio (SNR) performance of perpendicular media using a ring head without soft underlayer (SUL) and compared it with that of longitudinal media. With optimized exchange coupling of the media, the ring head shows good writability on the perpendicular media without SUL. At a linear density of 600 kfci, the ring head/perpendicular media essentially has no SNR gain over the longitudinal media, whereas going to 1000 kfci, the perpendicular media has an advantage of about 4 dB over the longitudinal. Comparison of the ring head (RH) without SUL was also made with the monopole head (MPH) and shielded pole head (SPH), both with SUL. RH and MPH both have about the same Stoner-Wohlfarth field gradient and SNR performance, whereas at the SNR plateau, SPH yields an SNR about 4-5 dB higher than RH and MPH, thanks to the high field gradient. Index Terms--Longitudinal recording, micromagnetic modeling, monopole head, perpendicular recording, ring head, shielded pole head, SNR, SUL.

Single pole perpendicular recording heads with track width below 100 nm have been examined using three-dimensional dynamic micromagnetic modeling, with focus on the dynamic field reversal and the head relaxation process. A head laminated through the thickness with the pole tip detached from the yoke shows very fast field response to the driving current, well repeatable domain configurations, instantaneous field relaxation after writing as well as robust near-zero remanent field. Index Terms--Micromagnetics, perpendicular recording, single pole head.

Wrap-around shielded writers combining both trailing shield and side shield have been studied both by modeling and by experiments. WAS design is demonstrated to have superior performance over its predecessor trailing shielded writer in perpendicular magnetic recording systems. While maintaining the down-track performance, the side shield significantly reduces the side fringing field, thus enabling high track densities. In this paper, various aspects ofWAS design are investigated. Issues unique to side shielded design such as near and far track erasure are also discussed in detail. An outlook of future PMR writer and recording systems design is presented at the end. [ABSTRACT FROM AUTHOR]

Presents a micromagnetic modeling on the readback process of perpendicular recording with soft underlayer (SUL). Effect of the SUL on readback; Transition response for different SUL saturation magnetization; Rolloff curves of the readback power with linear density for different values of medium thickness.