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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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High linear density in perpendicular recording

Davide Guarisco and Hai Nguy

J. Appl. Phys. 93, 6745 (2003); http://dx.doi.org/10.1063/1.1557713 (3 pages) | Cited 5 times

Online Publication Date: 9 May 2003

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Two kinds of perpendicular oxide media are compared with a conventional, boron-alloy media. Using an integrated, 245 nm wide, single-pole, high-Bsat writer with trapezoidal write pole, a linear density of 760 kfci at a BER of 10−5 was achieved at the ID radius of an oxide disk at 5400 RPM. MFM images of written tracks show higher-quality transitions up to a higher linear density on the oxide media. Furthermore, transitions on the B-alloy media exhibit a high degree of curvature. Finally, room temperature measurements of thermal decay on an improved oxide media, with only slightly degraded recording performance, showed the oxide media to be thermally stable. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Ak Magnetic properties of monolayers and thin films

Remanent head field study of single pole-type head based on micromagnetics

Masafumi Mochizuki, Chiaki Ishikawa, Hiroshi Ide, Kazuhiro Nakamoto, Yoshinobu Nakatani, and Nobuo Hayashi

J. Appl. Phys. 93, 6748 (2003); http://dx.doi.org/10.1063/1.1557714 (3 pages) | Cited 9 times

Online Publication Date: 9 May 2003

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The magnetization configurations within the pole tip of the single-pole-type head have been examined through a micromagnetic computer simulation based on the Landau–Lifshitz–Gilbert equation. The aspect ratio, including the effect of the exchange length (Lex), was defined as the ratio of the throat height (Th) to the write-track width (Tww) and the thickness (Tp), which is given (Th×Lex)/(Tww×Tp). It was found that the magnetization configuration and the perpendicular component of remanent head field (Hr) are strongly dominated by this aspect ratio at any value of Tww. It was also found that there is a characteristic aspect ratio at which Hr starts to decrease. These results show that decreasing the aspect ratio is an effective way to reduce the intensity of the remanent head field. © 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.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ss Magnetic recording materials

High anisotropy CoCrPt(B) media for perpendicular magnetic recording

Bin Lu, Dieter Weller, Ashwin Sunder, Ganping Ju, Xiaowei Wu, Richard Brockie, Tom Nolan, Charles Brucker, and Rajiv Ranjan

J. Appl. Phys. 93, 6751 (2003); http://dx.doi.org/10.1063/1.1557715 (3 pages) | Cited 4 times

Online Publication Date: 9 May 2003

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CoCrPt(B) media with high magnetic anisotropy have been fabricated at a thin magnetic layer thickness (10 nm) and a thin interlayer thickness (4 nm). The hard magnetic properties of the CoCrPt enable addition of boron, which aids to magnetically decouple the grains. These media are thermally stable and have an enhanced signal-to-noise ratio. © 2003 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.30.Gw Magnetic anisotropy
75.50.Cc Other ferromagnetic metals and alloys
75.70.Ak Magnetic properties of monolayers and thin films
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
68.60.Dv Thermal stability; thermal effects

Cross-track noise profile measurement for adjacent-track interference study and write-current optimization in perpendicular recording

Wen Jiang, Gautam Khera, Roger Wood, Mason Williams, Neil Smith, and Yoshihiro Ikeda

J. Appl. Phys. 93, 6754 (2003); http://dx.doi.org/10.1063/1.1557716 (3 pages) | Cited 14 times

Online Publication Date: 9 May 2003

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A cross-track noise profile measurement is developed for identifying the source of adjacent-track interference (ATI) fields in perpendicular recording systems. The noise amplitude as a function of cross-track position and write current clearly delineates the extent, magnitude, and polarity of stray fields under different portions of the head. Experimentally obtained stray field strength relative to writing field is in good agreement with finite element modeling. For given head and disk components, the composite picture of noise amplitude for both writing field and stray fields as a function of write current also provides a way of selecting an optimal write current with respect to the medium dynamic coercivity, saturation, and ATI threshold. Further investigation on the asymmetries in the noise profiles have led to two interesting discoveries. The first is an asymmetry in ATI field that can be attributed to the polarity of the radially oriented magnetization in the soft underlayer. The second is an artifact associated with the change in read head sensitivity around track edges due to fields from the dc-erased hard recording layer. © 2003 American Institute of Physics.
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75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Ak Magnetic properties of monolayers and thin films

Experimental study of playback giant magnetic resonance head nonlinearity in perpendicular recording

P. Luo, K. Stoev, F. Liu, A. Vadde, M. Gibbons, M. Lederman, and M. Re

J. Appl. Phys. 93, 6757 (2003); http://dx.doi.org/10.1063/1.1557717 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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In this article, nonlinear distortions of the playback giant magnetic resonance (GMR) sensor in perpendicular recording are characterized in both time and frequency domains. We use three perpendicular media with different Mrt (0.46, 0.6, and 0.8 emu/cm2) and two groups of similar magnetic-read width (MRW) but different junction type [contiguous junction (CJ) and lead-over-lay (LOL)] GMR heads. Square-wave patterns at moderate densities are recorded to minimize NLTS, partial erasure, and transition broadening effects. Both time- and frequency-domain measurements indicate that the LOL-type GMR heads show playback nonlinearity (7%–23%), while the CJ-type GMR heads do not. Micromagnetic simulation is utilized to understand the hard bias field with different junction designs. The result indicates that the hard bias (HB) field in LOL type (HB field ∼6.9 Oe) at the air bearing surface (ABS) and stripe center is much lower than that in CJ type (HB field ∼54.0 Oe). Therefore, the free layer with large HB–HB distance will be more susceptible to saturation. © 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.
85.70.Li Other magnetic recording and storage devices (including tapes, disks, and drums)
85.75.-d Magnetoelectronics; spintronics: devices exploiting spin polarized transport or integrated magnetic fields
02.30.-f Function theory, analysis

ΔM study of perpendicular recording media

X. W. Wu, R. J. M. van de Veerdonk, R. W. Chantrell, and D. Weller

J. Appl. Phys. 93, 6760 (2003); http://dx.doi.org/10.1063/1.1557718 (3 pages) | Cited 8 times

Online Publication Date: 9 May 2003

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A significant source of media noise in thin-film granular systems is intergranular exchange coupling. This important interaction between grains in longitudinal recording media has been studied by well-established ΔM(H) techniques. In this study, micromagnetic calculation using a Monte Carlo simulation has been carried out to confirm the validity of such a technique for perpendicular media. A recently developed demagnetization correction method is applied to a series of alloy perpendicular media, and subsequently, the exchange interactions in these films are studied using the ΔM(H) technique. With increasing film thickness, ΔM(H) changes from positive to negative, indicating a reduction of the exchange interaction in thicker films. This reduction is attributed to a stronger exchange coupling between grains at the initial stage of the film growth. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.40.Mg Numerical simulation studies
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.30.Et Exchange and superexchange interactions

Recording characteristics of perpendicular magnetic media with CoZrNb, NiFeNb, and exchange-pinned NiFeNb soft magnetic underlayers

Min Zheng, Albert Chekanov, Geon Choe, Kenneth E. Johnson, Lan Gao, and Sy-Hwang Liou

J. Appl. Phys. 93, 6763 (2003); http://dx.doi.org/10.1063/1.1557719 (3 pages)

Online Publication Date: 9 May 2003

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The recording performance of perpendicular media with amorphous CoZrNb, nanocrystalline NiFeNb, and exchange-pinned FeMn/NiFeNb soft magnetic underlayers (SULs) has been studied. A method has been proposed to quantify the spike noises from the SUL. We found that media with higher permeability NiFeNb SULs showed 4 db higher signal-to-noise ratio than media with lower permeability CoZrNb SULs. The exchange-pinned NiFeNb SUL suppresses spike noise and offers good recording performance. Furthermore, the recording frequency dependence of dynamic coercivity (Hc) was strongly affected by the use of different SULs. The increase in dynamic Hc with linear density is negligibly small for media with NiFeNb SULs, whereas dynamic Hc sharply increases with increasing density for media with CoZrNb SULs. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Gw Magnetic anisotropy
75.50.Kj Amorphous and quasicrystalline magnetic materials
75.50.Tt Fine-particle systems; nanocrystalline materials
75.30.Et Exchange and superexchange interactions
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Laminated nanocrystalline soft underlayers for perpendicular recording

Kiwamu Tanahashi, Atsushi Kikukawa, Yoshio Takahashi, and Yuzuru Hosoe

J. Appl. Phys. 93, 6766 (2003); http://dx.doi.org/10.1063/1.1557720 (3 pages) | Cited 5 times

Online Publication Date: 9 May 2003

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Media with laminated [Fe(Ta,Ti,Nb)C/Ta]n=2–4 soft magnetic underlayers (SULs) were prepared, and the effect of lamination on spike noise was investigated. Cross-sectional transmission electron microscopy observation revealed that nanocrystalline layers, composed of α-Fe grains with three-dimensional random orientation, were physically separated by 2.5-nm-thick Ta layers. Laminated SULs had low coercivities, i.e., less than 0.2 Oe, when the total thickness of the SUL ranged from 200 to 400 nm and the thickness of each nanocrystalline layer was more than 50 nm. These low coercivities are probably due to magnetostatic interaction between adjacent nanocrystalline layers. The medium with a laminated SUL showed much lower spike noise than the medium with a single-layer SUL. It is thought that magnetostatic interaction can reduce the stray field from the SUL, and result in a decrease in spike noise. © 2003 American Institute of Physics.
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75.50.Ss Magnetic recording materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.50.Tt Fine-particle systems; nanocrystalline materials
75.50.Bb Fe and its alloys
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Magnetic property control by using a composite template for dual-layered perpendicular media

Yoshihiro Ikeda, Kentaro Takano, Hoa Do, Natacha Supper, Andreas Moser, Yoshiaki Sonobe, and Philip Rice

J. Appl. Phys. 93, 6769 (2003); http://dx.doi.org/10.1063/1.1557816 (3 pages) | Cited 2 times

Online Publication Date: 9 May 2003

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Thin composite template layers for dual-layered perpendicular media have been studied. By combining a thin amorphous layer and a thin NiAl seed-layer, thermally stable and low noise media have been realized simultaneously. By changing the thickness ratio of the top amorphous layer and the bottom seed-layer, the magnetic properties of the recording layer can be controlled without changing the magnetic spacing between the soft underlayer and the write pole. Magneto-optical Kerr effect, transmission electron microscopy, and spin-stand measurements were performed to investigate the influence of different composite templates on the recording properties. It will be shown that the composite template allows the optimization of thermal stability and media noise in perpendicular media. The thermal stability of the media was measured by signal decay measurement using a spinstand and dynamic coercivity measurements using the Kerr effect. The KuV/kBT values, as obtained by the latter method, are consistent with the signal decay data. Those results demonstrate that the presented dynamic coercivity measurement is a very useful method for evaluating the thermal stability of dual-layered perpendicular media. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
75.70.Ak Magnetic properties of monolayers and thin films
68.60.Dv Thermal stability; thermal effects
78.20.Ls Magneto-optical effects
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Evaluation of magnetic interactions in a double-layered perpendicular magnetic recording media using ferromagnetic Hall effects

Sarbanoo Das, Sok-hyun Kong, and Shigeki Nakagawa

J. Appl. Phys. 93, 6772 (2003); http://dx.doi.org/10.1063/1.1557817 (3 pages) | Cited 9 times

Online Publication Date: 9 May 2003

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A new method for evaluating magnetic interactions among particles in the recording layer (RL) with a soft magnetic underlayer (SUL) in a double-layered perpendicular magnetic recording media has been demonstrated. Since the RL and SUL reveal Hall effect responses with different symmetries regarding the applied magnetic field, it is possible to not only detect the anomalous Hall voltage from the RL and the planar Hall voltage from SUL simultaneously, but also to extract and evaluate their properties individually. In order to evaluate the magnetic interparticle interactions in the RL, an evaluation index of the ΔV-plot, which corresponds to the ΔM-plot, estimated using a simple relation among the initial magnetization curve, the upper and lower branch of the major hysteresis loop, was introduced. The initial magnetization curve of Co–Cr–Ta RL in a Co–Cr–Ta(100 nm)/Ni–Fe(50 nm) double-layered thin film, can be evaluated from the Hall voltage in positive and negative range of applied magnetic field using the point symmetry of the anomalous Hall voltage revealed by the RL. The negative peak in the ΔV-plot of the double layer indicated the dominance of magnetostatic interaction in the Co–Cr–Ta layer. Measurements under the canted applied field revealed field direction dependence in the estimated ΔV-plot. Adjustment of the driving current direction with respect to the in-plane projection of the applied magnetic field was found to be effective for selective rejection of the contribution from the SUL to the total Hall effect signal. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.70.Ak Magnetic properties of monolayers and thin films
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.50.Cc Other ferromagnetic metals and alloys
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Characterization to realize CoCr-based perpendicular magnetic recording media with high squareness and normalized coercivity

Shin Saito, Fmikazu Hoshi, Norikazu Itagaki, and Migaku Takahashi

J. Appl. Phys. 93, 6775 (2003); http://dx.doi.org/10.1063/1.1557818 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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In an attempt to find a material guidance to realize CoCr-based perpendicular media with high squareness and normalized coercivity, we have performed systematic magnetic characterization to examine the effects of thermal agitation and magnetic exchange interaction. The main results are as follows: (1) With decreasing measuring temperature from R. T. to 4.2 K, normalized coercivity, Hc/Hkgrain, increases for the medium strongly influenced by thermal agitation, whereas changes slightly for the medium with strong intergranular exchange coupling. (2) All the media characterized in this study have a low value of Hc/Hkgrain equal to or less than 0.36 at R. T. (3) An exchange decoupled medium (α=1.0) tends to show a large positive Hn/Hkgrain, which results in a significant decrease of loop squareness S. On the other hand, it is possible to obtain a medium with S=1 for α>1.6 through the exchange interaction. (4) To realize a medium with S=1 and α as small as possible, selection of material with 4πMs/Hkgrain=0.2 (for α=1.6) is promising. On the other hand, to realize a medium with Hc/Hkgrain as high as possible, selection of material with 4πMs/Hkgrain=0.70 (for α=1.3) is favorable. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
75.30.Et Exchange and superexchange interactions
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.
81.15.Cd Deposition by sputtering
75.50.Cc Other ferromagnetic metals and alloys

Improvement of soft magnetic properties of Fe–Co–B underlayer with large saturation magnetization by Ni–Fe–O seedlayers

Sok-hyun Kong, Takeshi Okamoto, and Shigeki Nakagawa

J. Appl. Phys. 93, 6778 (2003); http://dx.doi.org/10.1063/1.1557753 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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Fe–Co–B layers were investigated for a soft magnetic underlayer with large saturation magnetization 4πMs in perpendicular magnetic recording media. The addition of B was examined to see the decrease of in-plane coercivity Hc∥ in the Fe–Co layer. The surface morphology of the films observed by atomic force microscopy revealed that each of the grains in the Fe–Co–B layer seemed to be separate. These separate grains seemed to cause the suppression of exchange coupling between grains in polycrystalline ferromagnetic films. A Ni–Fe–O seed layer was effective in reducing the grain size of the Fe–Co–B layer and inducing high uniaxial in-plane magnetic anisotropy. The grain size of the Fe–Co–B layer deposited on the Ni–Fe–O seedlayer was about 73% that of a Fe–Co–B single layer. The magnetic anisotropy field Hk was as high as 255 Oe in the Fe–Co–B/Ni–Fe–O layer. Furthermore, the relative permeability μr of Fe–Co–B/Ni–Fe–O was about 200 and the resonance frequency fr was above 3 GHz. Insertion of a Ni–Fe–O interlayer was also effective in decreasing Hc∥ of the Fe–Co–B layer. A [Fe–Co–B/Ni–Fe–O]8 multilayer exhibited Hc∥ as low as 11 Oe in the hard axis of magnetization. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.50.Bb Fe and its alloys
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.70.Ak Magnetic properties of monolayers and thin films
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
75.30.Gw Magnetic anisotropy

Oxide seed layer with low surface energy to attain fine grains in magnetic layers

S. H. Kong, K. Mizuno, T. Okamoto, and S. Nakagawa

J. Appl. Phys. 93, 6781 (2003); http://dx.doi.org/10.1063/1.1557754 (3 pages) | Cited 5 times

Online Publication Date: 9 May 2003

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The relationship of surface energy γs to the seed layers, grain size, and crystallite orientation of the recording layer is discussed. The oxide seed layer with lower γs is effective in attaining fine grains in magnetic upper layers. The grain size of a Co–Cr–Ta recording layer deposited on an oxide seed layer with lower γs is about 50% that of a recording layer deposited on a metallic seed layer with higher γs. The reduction in grain size in the recording layer with a Ni–Fe–O seed layer led to suppression of the noise level in the high recording density region. Furthermore, the grain size of the Fe–Co–B soft magnetic layer on the oxide seed layer with 27 mN/m γs, which corresponds to 75%–50% that of metallic films, also reduced to about 70% that of the Fe–Co–B single layer. The material of the magnetic upper layer on the seed layer with low γs may consist of very small dense island grains in the region of initial film growth, due to its high diffusion energy. These small dense nucleation sites in the region of initial growth may reduce the grain size. © 2003 American Institute of Physics.
Show PACS
75.50.Ss Magnetic recording materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
68.35.Md Surface thermodynamics, surface energies
68.35.Fx Diffusion; interface formation
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