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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Effect of reader saturation on the measurements of NLTS in perpendicular recording

Jian Chen, Wenzhong Zhu, Juan Fernandez-de-Castro, and Dean Palmer

J. Appl. Phys. 93, 6534 (2003); http://dx.doi.org/10.1063/1.1557933 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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In perpendicular recording, the magnetostatic interaction delays the second transition in a dibit, giving rise to a positive nonlinear transition shift (NLTS) in the written magnetization pattern. However, when the reader becomes saturated, the measured NLTS can take on negative values. Two different techniques to measure NLTS are simulated using a self-consistent recording model: (1) the fifth-harmonic cancellation and (2) dipulse extraction from pseudorandom sequence. The measured NLTS from both techniques is shown to be affected by reader saturation. © 2003 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)

Analyses of the effect of head imaging on medium demagnetization field in perpendicular recording

Hong Zhou, Kaizhong Gao, and H. Neal Bertram

J. Appl. Phys. 93, 6537 (2003); http://dx.doi.org/10.1063/1.1558186 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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Poisson’s equation is solved exactly to obtain the medium demagnetization field for both a single pole head and a single pole with a trailing shield (shielded single pole) head designs in perpendicular recording. To write an isolated transition, for the semi-infinite single pole head, head imaging can be neglected when calculating the demagnetization field. To the semi-infinite shielded single pole head, when the pole separation is reduced, perfect imaging from both the head and the soft magnetic underlayer is a good approximation. © 2003 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Stitched pole-tip design with enhanced head field for perpendicular recording

Daniel Z. Bai and Jian-Gang Zhu

J. Appl. Phys. 93, 6540 (2003); http://dx.doi.org/10.1063/1.1557935 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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A perpendicular write head with a stitched pole tip and side yoke recessed from the air-bearing surface is proposed and investigated using three-dimensional micromagnetic modeling. The design yields an increase of head field magnitude by 30% over the conventional single pole head. It is found that the optimal flare angle at the bottom of the yoke is 45°, for maximizing the on-track field magnitude and getting the minimum off-track field at the same time. Reducing the throat height significantly increases on-track field, while the off-track field increases as well. Lamination of the pole tip is necessary for producing robust zero remanent field for deep-submicron track widths. Introducing adequate transverse anisotropy in the head will significantly shorten the relaxation time of the magnetic moments after writing with little degradation on write efficiency. © 2003 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Effect of pole tip anisotropy on the recording performance of a high density perpendicular head

Mohammed S. Patwari, Sharat Batra, and R. H. Victora

J. Appl. Phys. 93, 6543 (2003); http://dx.doi.org/10.1063/1.1555377 (3 pages) | Cited 8 times

Online Publication Date: 9 May 2003

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A perpendicular recording head for an areal density of 1 Tbit per square inches has been developed using a self-consistent three-dimensional (3D) micromagnetic model. The soft underlayer and the recording layer have been included in the model. The head consists of a probe type tip protruding from a collar. The tip has saturation magnetization (Ms) of 24 kG while the collar has lower Ms of 10 kG. The magnitude and orientation of anisotropy field (Hk) in the tip is varied to obtain the best recording performance. A perpendicularly oriented Hk in the tip reduces flux spreading, thereby enhancing the recording field in the writing track while reducing the offtrack field. However, simulations show that the head’s performance suffers in terms of high remanent field and slower frequency response. Simulations show that a lower remanent field can be achieved by applying ac demag pulse to the tip. A detailed comparison has been made between two cases of perpendicular Hk of 1 kOe and longitudinal Hk of 10 Oe in the tip of the head. Results show a clear tradeoff in terms of recording field and frequency response. Finally, simulations show that the designed head is capable of recording areal density of 1 TBPSI on a recording layer of Ms of 700 emu/cc, thickness of 20 nm, Hk of 18 kOe and average grain diameter of 6 nm. © 2003 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.30.Gw Magnetic anisotropy
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Design of multisurface single pole head for high-density recording

S. Takahashi, K. Yamakawa, and K. Ouchi

J. Appl. Phys. 93, 6546 (2003); http://dx.doi.org/10.1063/1.1561793 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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Design of multisurface single pole heads was studied for obtaining a proper recording field profile to meet medium magnetic properties. By locating the bump core at the trailing edge of the base core, field gradient could be much improved compared with the bump core located at the center of the base core. Fields from both the bump and base cores could be individually adjusted by changing their dimensions. A large bump height with a large magnetomotive force could provide both the highest field. The multisurface single pole head which could be adapted to a wide range of medium magnetic properties, such as, a saturation field of 12 kOe and a negative nucleation field of 7 kOe for 200 Gb/in.2 recording. The bump height of 100 nm can provide the maximum field larger than 12 kOe along with the base core field less than 7 kOe and the field gradient larger than 180 Oe/nm. © 2003 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Energy surface model of single particle reversal in sub-Stoner–Wohlfarth switching fields

Kai-Zhong Gao, Eric D. Boerner, and H. Neal Bertram

J. Appl. Phys. 93, 6549 (2003); http://dx.doi.org/10.1063/1.1555378 (3 pages) | Cited 20 times

Online Publication Date: 9 May 2003

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A simple energy surface model is introduced to explain single domain particle switching under sub-Stoner–Wohlfarth fields. The criterion is that if the initial energy exceeds the subsequent energy barrier maximum, then the particle can reverse. Reversal will occur only for small damping constants and short field rise times, so the magnetization dynamics explores a sufficiently large portion of the energy surface. The results are confirmed by micromagnetic analyses and are consistent with both large scale micromagnetic simulation and experimental data. This effect may be utilized for ultrahigh density (1 Tbit/in2) and ultrahigh data rate magnetic recording (>2 Gbit/s). © 2003 American Institute of Physics.
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75.40.Mg Numerical simulation studies
75.50.Ss Magnetic recording materials
75.60.Jk Magnetization reversal mechanisms
75.50.Tt Fine-particle systems; nanocrystalline materials

Demonstration and characterization of 130 Gb/in2 magnetic recording systems

K. Stoev, F. Liu, Y. Chen, X. Dang, P. Luo, J. Chen, J. Wang, K. Kung, M. Lederman, M. Re, G. Choe, J. N. Zhou, and M. Yu

J. Appl. Phys. 93, 6552 (2003); http://dx.doi.org/10.1063/1.1540138 (3 pages) | Cited 9 times

Online Publication Date: 9 May 2003

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We have successfully demonstrated longitudinal recording at areal density of 130 Gb/in2 at a data rate as high as 170 Mbps (21 MB/s) and at a bit-aspect-ratio (BAR) of 2.9, using merged inductive-write/spin-valve-read heads on low noise thin film disks. The heads were fabricated with the standard photolithography and wafer pole trimming used in our currently available commercial products. The reader is a bottom synthetic spin valve (BSSV) with a 0.09 μm gap, and the writer has a conventionally trimmed pole with 0.09 μm gap. The reader magnetic read width (MRW) was measured at 0.10 μm. At read bias of ∼4 mA we measured reader sensitivity as high as 20 mV/μm. The write head was also optimized for tracks as narrow as 0.14 μm operating at overwrite (OW) of 36 dB and nonlinear transition shift (NLTS) better than −25 dB at 610 kBPI, without precomp. Using conventional media we measured total spectral SNR∼18 dB. The media to electronics noise ratio was 4.8, showing that we are still operating in a media noise limited system. Low-flying air bearing surface (ABS) design and advanced pole tip recession (PTR) control were required to achieve magnetic spacing of about 15 nm. © 2003 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Evaluation of high data rate disk drive recording subsystem

David Kaiser, Housan Dakroub, Al van der Schans, Elzbieta Haftek, Shaoping Li, Wenzhong Zhu, John Pro, Ko Vorasarn, Andrzej Stankiewick, Richard Cox, Yan Liu, Huaan Zhang, Karstan W. Radish, Klarquest, Sarit Sharma, et al.

J. Appl. Phys. 93, 6555 (2003); http://dx.doi.org/10.1063/1.1543123 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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An effort has been made to evaluate disk drive components at high data rates. Fully functional write-head/media components to 2.6 Gbit/s have been demonstrated in spin-stand testing and magnetic force microscopy characterizations. In addition, the drive front-end electronics examined possess complete functionality up to 4.0 Gbit/s without significant performance degradation, which is consistent with electric modeling results. Furthermore, our experimental data clearly indicate that the pre-amp’s performance at high frequency is becoming a limiting factor to achieving an ultrahigh data rate in present write-head/media designs. The magnetic moment on write gap edges for certain recording heads shows signs of becoming insensitive to following the write current switching speed at ultrahigh frequency. © 2003 American Institute of Physics.
Show PACS
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
85.75.Bb Magnetic memory using giant magnetoresistance
68.37.Rt Magnetic force microscopy (MFM)

Longitudinal write-process modeling including measured angular-dependent coercivity

Terry Olson, Wenchien Hsiao, and Danzhu Lu

J. Appl. Phys. 93, 6558 (2003); http://dx.doi.org/10.1063/1.1555379 (3 pages)

Online Publication Date: 9 May 2003

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Recent angular VSM measurements indicate that the remanent coercivity of various types of longitudinal media has an applied field angular dependence that approximates the behavior of Stoner–Wohlfarth particles with easy axes oriented isotropically in-plane. This is in contrast to the Kondorsky style switching (in-plane field, domain wall switching) inherently assumed in most models of the write process. In this article, we incorporate the measured angular dependent switching into a Williams–Comstock style write model. We find that the vertical spacing dependence of the transition width or “a” parameter can be much lower than that expected when only the in-plane component of the head field participates in switching the media. This phenomena is verified experimentally by writing at different spacings and reading at a constant spacing. We find that the experimental data can only be matched if the measured angular dependent switching is taken into account. © 2003 American Institute of Physics.
Show PACS
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ss Magnetic recording materials
75.50.Tt Fine-particle systems; nanocrystalline materials
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.40.Mg Numerical simulation studies

Pole tip protrusion study of various magnetic-head designs using finite-element analysis techniques

Arshad Alfoqaha and Kenneth Young

J. Appl. Phys. 93, 6561 (2003); http://dx.doi.org/10.1063/1.1558187 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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This article delineates the finite-element modeling techniques used in modeling four different magnetic head designs: (1) the flat-top pole, (2) the pedestal-defined-zero-throat, (3) the pedestal-defined-zero-throat-extended and (4) the stitch pole. We discuss the assumptions used in modeling the heads, the boundary conditions, meshing the geometry, and the type of analysis selected to perform the computations. Pole tip protrusion (PTP) results obtained for the heads were compared to see which design performs better under both current heating and ambient heating conditions. Results showed that the nine-turn stitch pole design does not perform as well as the other head designs in terms of PTP for current heating and ambient heating. This is due, among other reasons, to the existence of two layers of high coefficient of thermal expansion (CTE) photoresist material instead of one layer, and due to the fact that the lower photoresist in the apex region of the first insulation layer is very close to the ABS. Given the task of improving the PTP performance of the stitch pole design, we will show results on the implementation of partially or fully replacing the photoresist in the first and second insulation layers with alumina, or any appropriate material that has a low CTE. © 2003 American Institute of Physics.
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85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
65.40.De Thermal expansion; thermomechanical effects
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