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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.

The effect of stress-induced anisotropy in soft magnetic films on the in-plane anisotropy is examined. The simulation results for Fe65Co35 film elements with equal compressive stress show maze-like stripe domains representative of perpendicular anisotropy.

A micromagnetic modeling of a stitched pole-tip head that has enhanced head field over a transitional SPT head is discussed. The pole-tip lamination is essential to ensure a robust near-zero remanent field.

A single spin, a many-spin system such as a ferromagnetic thin film at zero energy damping can still reverse its magnetic moment and minimize the Zeeman energy while generating spin waves as an energy reservoir. The roll-off frequency reaches a maximum at the optimum current rise time and it is damping constant dependent .

A full 3D micromagnetic model for a perpendicular single pole head along with a soft magnetic underlayer for deep submicron track width dimensions is presented. It is found that at deep submicron track width, the maximum head field inside the medium is significantly smaller than the ideal value at any practical ABS-to-SUL separation, making the perpendicular recording much less attractive.

Magnetization dynamics during field reversal in thin film recording heads are studied via micromagnetic modeling. It is found that head field reversal under the current field can be characterized by two stages: an initial stage that is mainly governed by the gyromagnetic motion and virtually independent of energy damping, followed by a damping stage that strongly depends on the energy damping constant. Due to the finite energy damping in practical recording heads, the head field amplitude will roll off at high recording frequencies. Simply decreasing the current rise time or increasing current amplitude will not alleviate the situation, but rather worsen it. There exists an optimum current rise time at which the head field rise time is minimized and the roll-off frequency is maximized. [ABSTRACT FROM AUTHOR]

A micromagnetic simulation is conducted to study the write field dynamics in the presence of antiferromagnetic exchange coupling (AFC) of writer pole for a perpendicular magnetic recording (PMR) writer head. It is found that, depending on the actual configuration of the AFC coupling in the yoke and the pole tip, there could be an intermediate transient state near zero write field during the magnetization reversal, compared to the normal writer design without AFC coupling. This transient state may cause recording performance degradation. We further investigated the AFC coupling effect on the remanent field in the degauss process. For different performance aspects, i.e., field dynamics, maximum field, and remanent field, the AFC in the yoke and in the pole tip plays different roles. [ABSTRACT FROM AUTHOR]

In this paper, finite element method (FEM) solving Maxwell's equations is used to study writer head design with side shields. A half side shielded writer is investigated due to the belief that writer designs with larger side fringing field can be accommodated in shingled recording. It was found that although a half side shielded writer provides higher on track field, curvature at track edge is also increased. The increasing curvature poses a limit on the writer pole width increment. Designing a writer to maintain low curvature while obtaining high on-track field continues to be the challenge for shingled recording. This paper explores a full range of writer design parameters using finite element modeling and introduces several design features for a wrap-around shielded writer. [ABSTRACT FROM PUBLISHER]

The characteristics of spatial and temporal field distributions are presented for wrap-around-shielded perpendicular magnetic recording writers. Micromagnetic modeling simulations are conducted to study the effects of shield thickness and the magnetization on the shield-related side field. An improvement of side field is found with the thicker shield thickness and higher saturation magnetization. The maximum side field is spatially and time dependent during the dynamic writing process. The side field reaches the maximum around the transitions, where the write field from the main pole is at the minimum. In addition, the write current rise-time effect on the side field is investigated. [ABSTRACT FROM PUBLISHER]

This paper presents a study of the degauss process of a perpendicular magnetic writer pole using micromagnetic modeling as a tool. The dynamics of the yoke and the pole-tip magnetization relaxation during degauss are studied in detail, and the remanent field of the pole tip is used as a metric to measure the effectiveness of each of the degauss methods. Various aspects of the degauss current waveforms are investigated, such as frequency, duration, initial current amplitude, amplitude decay envelope, and overshoot. Some alternative waveforms, i.e., unipolar reverse pulse degaussing, have also been examined. It has been found for many of the parameters to have an optimal range outside of which the degauss effectiveness and efficiency are degraded. [ABSTRACT FROM AUTHOR]

Abstract: Micromagnetic models of side shielded perpendicular magnetic recording heads show detailed magnetization configuration of the trailing and side shield during the dynamic writing process. The calculation result indicates possible origins of three kinds. The leakage field at the side shield edge, the side shield saturation, and trailing and side shield domain switching. The side shield edge and the saturation induced fields are based on the geometric boundary and they are limited to just around the side shield edge. However the shield switching field can spread to far track position from the side shield to the trailing shield, and it originates from magnetic boundary of the domains and wall formed during the dynamic writing process. As a result, it produces bump field at far track positions in some trailing and side shields. [Copyright &y& Elsevier]

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.

A computational study of the head field was presented in a specific head/media configuration, where the intermediate layer (IL) consists of the periodic magnetic columns and Ru columns. It was found that the head field increases with the thicker and wider magnetic columns. Micromagnetic simulation shows that this approach is to achieve a lower effective IL thickness for enhancing the write field by replacing some Ru grains with the columnar magnetic material without reducing the IL thickness. [ABSTRACT FROM AUTHOR]

We present a systematic study of write field asymmetry by using micromagnetic modeling for a perpendicular magnetic recording (PMR) writer structure. Parameters investigated include initial magnetization condition, write current amplitude, write current frequency, and initial write current polarity. It is found that the write current amplitude and frequency (data rate) are the dominant factors that impact the field asymmetry. Lower write current amplitude and higher write current frequency will deteriorate the write field asymmetry, causing recording performance (such as bit error rate) degradation. [ABSTRACT FROM AUTHOR]