Journal of the Magnetics Society of Japan

Magnetization Behavior in Ferro/Antiferromagnetic Exchange-Coupled Films (Review)

H. Fujiwara, C. Hou, M. Sun, H.S. Cho

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_1-8
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_1

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The complementary nature of the exchange-bias field and coercivity enhancement in ferromagneic (F) antiferromagnetic (AF) exchange-coupled layer systems is explained based on an extended Fulcomer & Charap's model, in which the directional distribution of the easy axes plays a decisive role in governing the magnetization behaviors. The model was further extended to deal with the AF-layer thickness ranging from zero to infinity, taking into account of Neel's spin-fanning model. A comprehensive explanation of the influence of exchange coupling on the magnetization behavior of the F-layer is given. It is shown that a rotational magnetzation process is inherent for the samples in which the exchange coupling effect is dominant. Varieties of phenomena are mostly ascribed to the existence of distribution in the magnetic properties, net spin moment at the AF-grain surface and AF-grain size.

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PRML Systems for Perpendicular Magnetic Recording Using a Double-Layered Medium

Hisashi OSAWA, Hiroyuki SUMIYOSHI, Yoshihiro OKAMOTO, Hidetoshi SAITO, ...

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_9-13
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_9

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The partial response maximum likelihood (PRML) systems characterized by the higher order polynomials for perpendicular magnetic recording using a double-layered medium are studied. The relationship between the required SNR to achieve a bit erorr rate of 10^-4 and a normalized linear density for (1,7)RLL and 16/17(0,6/6) coded PRML systems is obtained by computer simulation and compared with that of the conventional 16/17(0.6/6) coded EPR4ML system. The results show that among PRML systems discussed in this study the (1,7)RLL coded PR(1,2,3,3,2,1) ML,PR(1,2,1,0,-1,-2,-1)ML and PR(1,1,1,0,-1,-1,-1)ML systems and the 16/17(0,6/6) coded PR(1,2,3,3,2,1)ML,PR(1,3,4,4,3,1)ML and PR(1,2,1,0,-1,-2,-1)ML systems provide excellent performance and are superior to that of the 16/17(0.6/6) coded EPR4 ML system.

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Investigation of Perpendicular Recording Characteristics based on of Computer Simulations and Recording Tests.

H. Takano, Y. Nishida, A. Kuroda, Y. Yamamoto, H. Muraoka, Y. Nakamura

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_15-18
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_15

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An analytical method was developed for estimating the isolated transition length of perpendicular recording system using single-poletype head and double-layered medium. Recording characteristics were also examined for perpendicular system, and compared with the latest longitudinal recording system. Based on these examinations, recording conditions for achieving an areal recording density of 40 Gb/in ² were discussed.

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Design for low noise double layered perpendicular magentic medium

Kazuhiro OUCHI, Naoki HONDA, Jun ARIAKE

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_19-24
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_19

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Noise property and noise origin for double layered perpendicular magnetic recording media were studied in terms of the medium design and fabrication. It was found that medium noise from recording layer increased by introducing a soft magnetic backlayer. This might due to increase of a magnetic domain size of recording layer. In a Co-Cr system, some intermediate layers were found to reduce the medium noise of the recording layer. The still remained noise was thought due to the magnetization irregularity of the head-on like transition in the backlayer that was affected by the recording layer magnetization.

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BER Performance of PRML Channel Using Single-Layered Perpendicular Medium

Y. Okamoto, M. Akamatsu, T. Kanaoka, M. Sato, H. Saito, H. Osawa, N. H ...

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_25-28
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_25

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The bit-error rate (BER) performance of perpendicular magnetic recording using a single-layered medium is studied is studied. 16/17 (0, 6/6) code and (1, 7) RLL code are adopted as a recording code, and respectively combined with various PRML systems to achieve higher linear recording density. The results of read/write experiments using a spinstand show that the higher-order PRML systems such as E³ PR4ML and E⁴ PR4ML systems exhibit excellent BER performance.

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Recording Performance of Narrow-Trackwidth Perpendicular Recording Head

Kiyoshi Yamakawa, Kaori Taguchi, Kazuhiro Ouchi

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_29-33
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_29

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Narrow track perpendicular recording using single pole heads with FIB-trimmed main poles was studied. It was found that a 0.3 μm wide head exhibited recording saturation for a high coercivity (above 3000 Oe) perpendicular medium. MFM patterns of recorded tracks as narrow as 0.14 μm was observed for a linear density up to 400 kFRPI. The recorded trackwidth was found to be influenced by a stray field from dc-erasure or prerecorded magnetization around the recording track.

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Characterization of Perpendicular Magnetic Recording and Performance Estimation

H. Muraoka, K. Miura, Y. Sugita, Y. Nakamura

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_35-40
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_35

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Head/disk parameters of perpendicular magnetic recording to attain 100 Gbits/inch² was investigated. For a necessary readback pulse width of 70 nm, shield gab length, medium thickness, spacing and transition width were first determined. Then, for transfer function of the head condition, a maximum magnetic cluster size of a medium to satisfy a medium noise requirement was predicted from experimental results and theoretical noise consideration, which was 10 nm. Finally, a minimum perpendicular anisotropy for the medium to resist thermal fluctuation was also considered. The results indicated that particle, and cluster, diameter of 10 nm and anisotropy field of 15 kOe was necessary for media in order to attain 100 Gbits/inchi².

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Error Rate Performance of E²PR4ML System for Punctured Convolutional Codes

Hidetoshi SAITO, Yoshihiro OKAMOTO, Hisashi OSAWA

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_41-44
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_41

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As efficient recording codes for an extend class-4 partial response (E²PR4) system, the high rate punctured convolutional codes are proposed. These coding methods are based on deleting several symbols from an original low rate code. Therefore, these codes are decoded easy maximum likelihood (ML) algorithm for the original code. As a result, it is shown that the rate 32/33 punctured convolutional codes E² PR4ML have about 1.0 and 2.6 dB advantage over the conventional rate 8/9 maximum transition run and 16/17 (0,6/6) coded systems at a bit error rate of 10^-4. Furthermore, by using soft-output Viterbi decoding, the error rate performance of a punctured system is improved over the conventional Viterbi decoding method.

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Study on Medium Noise and Remanent Magnetization State for Single-Layer Perpendicular Magnetic Recording Media

T. Onoue, T. Asahi, T. Hirayama, J. Hokkyo, T. Osaka

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_45-48
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_45

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Correlation between media noise and the remanent magnetization states of perpendicular magnetic recording media, which have carbon or TiCr film as an underlayer, was investigated. A C60 medium, which has thick carbon (60nm) as an underlayer, showed lower dc-erased noise value than a Ti30 medium having a TiCr underlayer. MFM image of C60 medium at dc-erased state showed larger magnetic cluster but weaker intensity than the Ti30 medium. It is important for the C60 medium to make fine magnetic grain to obtain high reproduced output at high recording density.

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Magnetization Structures of Perpendicular Recording Medium under Magnetic Field

Yukio Honda, Yoshiyuki Hirayama, Atsushi Kikukawa, Masaki Futamoto

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_49-53
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_49

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MFM observations were carried out on a CoCr₁₉Pt₁₀ perpendicular medium by applying uniform magnetic fields to the sample. Nucleation of reverse magnetic domain was observed for an uniformly dc-magnetized sample at magnetic field as small as 0.6 kOe. With increasing the magnetic field, the number of reverse domain increased Pre-recorded magnetization transition structure with 20 kFCI recording remained unchanged even when the magnetic field was increased up to around 4 Oke. This result clearly shows that the magnetic transitions are very stable, but reverse magnetic domains are easily formed between the recorded transitions under an influence of reverse magnetic field. The local fluctuation of perpendicular magnetic anisotropy in the medium seems to be related to the formation of reverse domains under the influence of demagnetizing field.

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ECR-sputter-deposited Co-Cr-Ta perpendicular recording disk

S. YAMAMOTO, T. IKEDA, K. HlRATA, H. KURISU, M. MATSUURA

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_55-58
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_55

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Sputtering method utilizing electron-cyclotron-resonance microwave plasma was used to fabricate Co-Cr-Ta perpendicular magnetic recording disks. Ta addition was proved to be effective to increase coercivity and squareness in perpendicular direction of magnetic layer. A perpendicular recording disk with 60 nm thick Co-Cr-Ta layer showed superior signal-to-media noise ratio to a 4 Gb/in² longitudinal disk at densities higher than 90 kFRPI. Ti underlayer was effective to improve perpendicular orientation, and increase coercivity, squareness, high-density recording characteristics.

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Improvement of Crystallographic and Magnetic Characteristics of ultra-thin Co-Cr Films Deposited on Pt Underlayer

Shigeki Nakagawa, Atsushi Sato, Ichiro Sasaki, Masahiko Naoe

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_59-62
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_59

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Pt seed layer was effective to improve c-axis orientation of Co₇₇Cr₂₀Ta₃ layers deposited on it especially for higher substrate temperature T_s above 200°C. The 50 nm-thick Co₇₇Cr₂₀Ta₃ layer deposited at T_s of 250°C on Pt underlayer exhibited relatively large perpendicular coercivity H_c⊥ around 2.5 kOe. Anomalous Hall measurement implied that the Co₇₇Cr₂₀Ta₃/Pt bilayered film did not have transition layer, which possessed worse c-axis orientation at the interface. Pt seed layer is effective to deposit the ultra-thin Co-Cr recording layer and improve its crystallographic and magnetic characteristics.

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A Design of Soft Magnetic Backlayer for Double-Layered Perpendicular Magnetic Recording Medium

Singo Takahashi, Kiyoshi Yamakawa, Kazuhiro Ouchi

1999 Volume 23 Issue S_2_PMRS_99 Pages S2_63-66
Published: 1999
Released on J-STAGE: December 15, 2011

DOIhttps://doi.org/10.3379/jmsjmag.23.S2_63

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NiFe/FeMn and NiFeCuMo/FeMn multilayers were studied for application to a soft magnetic backlayer of a perpendicular recording composite medium. The exchange-biased field in the lowest layer was enhanced by introducing an FeMn/Cu seedlayer so that controllability of the anisotropy field in each layer was obtained. The NiFe film with exchange-biased radial anisotropy may provide a low noise medium.

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