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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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High data rate recording: Moving to 2 Gbit/s

A. Taratorin, S. Yuan, and V. Nikitin

J. Appl. Phys. 93, 6444 (2003); http://dx.doi.org/10.1063/1.1557342 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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High data rate recording can be achieved using fast write drivers and fast heads. Advanced short-yoke write heads and write drivers with 450 ps rise time and programmable current overshoot were used to study recording at data rates up to 2 Gbit/s. The head flux rise time causes shifts of recorded transitions. It is well known that current overshoot helps to overcome bandwidth limitations in the write driver, interconnects, and write head. However, excessive overshoot may cause pattern-dependent transition shifts and significant distortions of recorded transitions. We present the data rate performance of short-yoke recording heads, analysis of nonlinear pattern-dependent distortions, and optimization of the write current wave form in the 1–2 Gbit/s range. Simple dibit and tribit patterns were recorded at 2 Gbit/s. Low-distortion recording for arbitrary data patterns was demonstrated at 1.6 Gbit/s after optimization of write current overshoot. © 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.
75.50.Ss Magnetic recording materials

Understanding field rise time and magnetic damping in thin film recording heads

Jian-Gang Zhu and Daniel Z. Bai

J. Appl. Phys. 93, 6447 (2003); http://dx.doi.org/10.1063/1.1557343 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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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. © 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.
75.60.Jk Magnetization reversal mechanisms

Writing at high data rates

K. B. Klaassen and J. C. L. van Peppen

J. Appl. Phys. 93, 6450 (2003); http://dx.doi.org/10.1063/1.1557344 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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The physical restrictions on the write signal path in a hard disk drive are such that, at high data rates, the write electronics typically need a large voltage supply and generates much heat. In addition, the electronics produce inadequate write current wave forms that adversely affect the magnetic patterns to be recorded. After a brief overview of what has been proposed to alleviate this problem, a solution is presented wherein a high inductance head (56 nH) can be driven up to 1 Gb/s. This is made possible by compensating the head inductance into (nearly pure) resistance and matching this resistance to the characteristic impedance (75 Ω) of the 5 cm long driver-to-head interconnect. This compensation/matching only requires small, lossy capacitors, which can be implemented in the head-processing phase onto the head wafers as an integral part of head processing. © 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.
75.50.Ss Magnetic recording materials

Write-to-read coupling study of various interconnect types

Eunkyu Jang and Xiaofeng Zhang

J. Appl. Phys. 93, 6453 (2003); http://dx.doi.org/10.1063/1.1557345 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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The use of suspension interconnects has brought about a great concern for the coupling of the write signal into read lines during write operations. The cross-talk coupling can result in amplitude degradation of giant magnetoresistive (GMR) element at high data rates. In this study, write-to-read couplings of GMR heads during writing operations are studied as a function of write frequency for various interconnects. The coupling current of interconnects with a ground plane is 2–3 times smaller than interconnect without the ground plane. It was found that the ground plane is more important in write-to-read coupling than separation between write and read traces. © 2003 American Institute of Physics.
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85.75.Bb Magnetic memory using giant magnetoresistance
75.47.De Giant magnetoresistance
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.30.Et Exchange and superexchange interactions

Adjacent track encroachment analysis at high track density

Zhihao Li, Mike Schaff, Rolf Munson, Mark Jurisch, Ted Noonon, Shaoping Li, and Yuming Zhou

J. Appl. Phys. 93, 6456 (2003); http://dx.doi.org/10.1063/1.1557651 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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The issue of adjacent track encroachment (ATE) has been studied for high track density (TPI) situations. Several techniques and methods have been utilized to determine the root cause of the adjacent track erasure. The new encroachment mechanisms, differing from those reported previously, have been identified for several different cases. It was found that the write-head gap edge corner or shoulder can generate a sizable fringing field, leading to measurable adjacent track encroachment problems in certain conditions. This type of side-erasure problem is not only associated with the amplitude and frequency of the writing current, but is also skew sensitive, depending upon both skew angle and skew polarity. Furthermore, finite element calculations confirm that in the vicinity of the notch corner, the fringing field strength could be as much as 4000 Oe. Experimentally it was also found that the side-erasure process induced by the notch shoulder was asymmetric in some situations. © 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.

Effects of focused-ion-beam irradiation on perpendicular write head performance

Chang-Min Park, James A. Bain, Thomas W. Clinton, and Paul A. A. van der Heijden

J. Appl. Phys. 93, 6459 (2003); http://dx.doi.org/10.1063/1.1557652 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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The effects of focused-ion-beam (FIB) irradiation on writer performance were examined on a perpendicular recording system. The entire top pole was irradiated by FIB with ion doses from 0 to 300 pC/μm2. PW50 and signal to noise ratio (SNR) were characterized using a spin stand before and after FIB irradiation. It was found that there is degradation of PW50 and SNR due to FIB irradiation. At the maximum dose (300 pC/μm2), PW50 increased by 33 nm (>30%) and SNR decreased by 5 dB (>25%). The degradation was attributed to the physical pole tip recession and the formation of a magnetic dead layer. The thickness of the magnetic dead layer was estimated by analyzing the write spacing loss. Using atomic force microscopy and stage current change monitored during FIB process, it was found that the entire 4-nm protective carbon layer was etched away with a dose of 25 pC/μm2. This result implies that the degradation with ion doses <25 pC/μm2 is exclusively due to damage to the magnetic layer at the pole surface due to Ga implantation. It was found that our experimental results are consistent with the conventional write spacing loss behavior. © 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.
75.50.Ss Magnetic recording materials
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.80.Jh Ion radiation effects
68.49.Sf Ion scattering from surfaces (charge transfer, sputtering, SIMS)

Influence of underlayers on the soft properties of high magnetization FeCo films

H. S. Jung, W. D. Doyle, and S. Matsunuma

J. Appl. Phys. 93, 6462 (2003); http://dx.doi.org/10.1063/1.1557653 (3 pages) | Cited 35 times

Online Publication Date: 9 May 2003

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A remarkable reduction in coercivity Hc was found in sputtered Fe65Co35(=FeCo) films on Cu, NiFe, Ru, Ta/Cu, Ta/NiFe, or Cu/IrMn underlayers. A decrease in Hc from 120 to 7–12 Oe was observed for Cu, NiFe, and Ru underlayers as thin as 2.5 nm but less for Ta. A Cu underlayer significantly reduced the maximum anisotropy fields from 2 kOe to 40 Oe, resulting in a well-defined in-plane average uniaxial anisotropy field Hk∼30 Oe. The saturation magnetostriction with Cu was (47±4)×10−6, independent of Cu and FeCo thicknesses. In-plane tensile film stress decreased with underlayer thickness tUL from 2 to 0.2 GPa but much less rapidly than the reduction in Hc. All underlayers induced a (110) texture in FeCo, which was strongest with Ta. Transmission electron microscopy of cross-sections showed an unusually long range coherence with low angle grain boundaries in the FeCo without an underlayer. Clear columnar grains were visible with all underlayers with an average grain size of ∼50 nm with Ta dropping to 9–10 nm for Cu, NiFe, and Ru. This alone is sufficient to explain quantitatively the reduction in Hc using Hoffmann’s ripple theory. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
81.15.Cd Deposition by sputtering
75.30.Gw Magnetic anisotropy
75.80.+q Magnetomechanical effects, magnetostriction
61.72.Mm Grain and twin boundaries
68.55.-a Thin film structure and morphology

Transverse field anneal studies of high moment FeCoB and FeCoZr films

M. Kevin Minor and Timothy J. Klemmer

J. Appl. Phys. 93, 6465 (2003); http://dx.doi.org/10.1063/1.1557346 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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Ever increasing areal densities have driven the need for high moment materials with large saturation magnetizations greater than 2 T. In addition, for applications such as write poles and soft underlayers, the high moment materials must exhibit soft and uniaxial magnetic properties which are thermally stable during high temperature processing. In this work, we examine 2.1 T FeCoB and 1.8 T FeCoZr films which are amorphous in the as-deposited state. The films are given longitudinal field anneals (LFAs) at 220 and 250 °C for 4 h. FeCoZr films remain amorphous after the 220 and 250 °C LFAs. FeCoB films remain amorphous after the 220 °C LFA, however, the 250 °C LFA results in crystallization in the FeCoB film. This crystallization is accompanied by a degradation in soft magnetic properties. As-deposited and 220 and 250 °C LFA FeCoB and FeCoZr films are then given transverse field anneals (TFAs) at 150 °C. As-deposited FeCoB and FeCoZr experience a 90° rotation of Hk or switching after less than 2 h of TFA. LFAs result in improved thermal stability in all FeCoB and FeCoZr films. The crystalline FeCoB film given a 250 °C LFA exhibited the best thermal stability, however, the magnetic properties were not optimal due to crystallization. © 2003 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
68.60.Dv Thermal stability; thermal effects
75.60.Nt Magnetic annealing and temperature-hysteresis effects
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Kj Amorphous and quasicrystalline magnetic materials
64.70.K- Solid-solid transitions
68.55.-a Thin film structure and morphology
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Anisotropy dispersion effects on the high frequency behavior of soft magnetic Fe–Co–N thin films

N. X. Sun and S. X. Wang

J. Appl. Phys. 93, 6468 (2003); http://dx.doi.org/10.1063/1.1557347 (3 pages) | Cited 6 times

Online Publication Date: 9 May 2003

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The high frequency behavior beyond 1 GHz of a Fe–Co–N film and a NiFe\Fe–Co–N film [NiFe stands for Ni81Fe19(wt. %)], shown as promising magnetic write head materials previously, has been investigated using a pulse inductive microwave magnetometer in this work. The NiF\Fe–Co–N film, which has a smaller dispersion angle (∼0.8°) than the Fe–Co–N film (∼2°), shows a smaller damping parameter and a higher ferromagnetic resonance frequency when longitudinally biased. When the Fe–Co–N film is transversely biased, the damping parameter of the Fe–Co–N film shows a diffuse peak at a transverse field of 1.76 kA/m (22 Oe), and its ferromagnetic resonance frequency shows a small local maximum at 1.76 kA/m (22 Oe). In contrast, the damping parameter of the NiFe\Fe–Co–N film shows a sharp peak at a transverse field of 1.4 kA/m (18 Oe), and its ferromagnetic resonance frequency displays a sharp local maximum also at a transverse field of 1.4 kA/m (18 Oe) too, which is very close to the dc anisotropy field. The sharp peak in the ferromagnetic resonance frequency and the damping parameter of the NiFe\Fe–Co–N film is due to the generation of a higher order (very close to the second order) ferromagnetic absorption when the ac field is large compared to the net in-plane dc magnetic field. © 2003 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
75.50.Ss Magnetic recording materials
75.30.Gw Magnetic anisotropy
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Nitrogen-induced local magnetic and structural properties of sputtered FeAlN thin films

Y.-K. Liu, M. H. Kryder, D. H. Ryan, and Z. Altounian

J. Appl. Phys. 93, 6471 (2003); http://dx.doi.org/10.1063/1.1557348 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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Conversion electron Mössbauer spectroscopy (CEMS) and x-ray diffraction were used to study a series of rf-reactively sputtered FeAlN thin films with the goal of gaining insight into the origins of their uniaxial magnetic anisotropy (UMA) and the effect of sputtering conditions on its thermal stability. At N/Fe=4.6%(±0.5%), N goes into interstitial vacancies without significant reductions in the hyperfine field (Bhf) of the Fe but causing lattice expansions, leading to an increased linewidth in the CEMS spectra of the film while the sample has an in-plane UMA. Reducing the target-to-substrate spacing used in the deposition process does not affect the nitrogen content of the films but yields an increased CEMS linewidth reflecting larger disorder in the local Fe environment. Heavy N doping causes the phase transform into γ′-Fe4N, ϵ-Fe3N, and ζ-Fe2N phases. A well defined UMA exists in mildly doped FeAlN films when doped N atoms mostly occupy the interstitial sites while FeAl and heavily doped FeAlN films are either isotropic or weakly anisotropic. UMA and its thermal stability are therefore concluded to have a correlation with the local environment of the Fe structure induced by N doping. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
68.55.A- Nucleation and growth
75.70.Ak Magnetic properties of monolayers and thin films
81.15.Cd Deposition by sputtering
76.80.+y Mössbauer effect; other γ-ray spectroscopy
75.30.Gw Magnetic anisotropy
68.60.Dv Thermal stability; thermal effects
71.70.Jp Nuclear states and interactions
61.72.J- Point defects and defect clusters
61.66.Bi Elemental solids
61.66.Dk Alloys
64.70.K- Solid-solid transitions
75.50.Dd Nonmetallic ferromagnetic materials

High-Bs Fe–Co–Al–O soft magnetic films

Kazuhiko Shintaku, Kiyoshi Yamakawa, and Kazuhiro Ouchi

J. Appl. Phys. 93, 6474 (2003); http://dx.doi.org/10.1063/1.1557349 (3 pages) | Cited 21 times

Online Publication Date: 9 May 2003

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Fe–Co and Fe–Co–Al–O films were prepared by rf magnetron sputtering in an Ar-gas atmosphere. The coercivity (Hc) of the Fe–Co films was greatly decreased by a small amount of Al2O3 addition. However, a film thickness of more than 500 nm is necessary to obtain minimum the Hch (Hc in the hard-axis direction) of 5 Oe. Hch was greatly decreased by using a Ni–Fe underlayer of 0.5–12 nm, and was less than 1 Oe with film thicknesses ranging from 50 to 600 nm for Fe–Co–Al–O films. An amorphous Co–Zr–Nb soft magnetic underlayer was also examined to investigate influence of underlayer crystal structure. A Hch less than 1 Oe was realized for the samples with Co–Zr–Nb underlayer thickness of about 2 nm. Amorphous underlayer films were also effective in improving the soft magnetic properties of Fe–Co–Al–O films. It is finally concluded that combination of a small amount of Al2O3 addition and a soft magnetic underlayer film is essential to obtain small Hch with high saturation magnetic flux density of 2.4 T in a wide range of film thicknesses. © 2003 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Bb Fe and its alloys
81.15.Cd Deposition by sputtering
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
68.55.-a Thin film structure and morphology
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