The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
Hiroaki Muraoka - One of the best experts on this subject based on the ideXlab platform.
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Micromagnetic model simulation of spin-torque oscillator and write head for microwave-assisted magnetic recording — Spin injection layer with in-plane anisotropy
2018 International Applied Computational Electromagnetics Society Symposium (ACES), 2018Co-Authors: Yasushi Kanai, Simon John Greaves, Ryo Itagaki, Hiroaki MuraokaAbstract:Micromagnetic simulations were carried out to obtain stable oscillation of a spin transfer torque oscillator (STO) inserted into the gap between the Main Pole and trailing shield of a write head. We assumed a spin injection layer with in-plane anisotropy. Results show that reducing the magnetostatic interaction between the write head and the STO is the key to obtaining stable STO oscillation.
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Microwave-Assisted Shingled Magnetic Recording
IEEE Transactions on Magnetics, 2015Co-Authors: Simon John Greaves, Yasushi Kanai, Hiroaki MuraokaAbstract:Simulations of shingled, microwave-assisted magnetic recording were carried out. First, a simplified model of the head field near the corner of the Main Pole of a write head was used to understand the effect of the spin torque oscillator (STO) position relative to the head. Next, shingled tracks were written and evaluated for two different write head and STO geometries. For shingled recording, locating a rotated STO on the side of the Main Pole may provide some advantages in that medium grains experience the high-frequency (HF) field for a longer time and the chirality of the HF field does not change as the grains pass by the STO. Recording simulations show that the rotated STO writes smoother track edges at lower densities, but there is little difference in signal-to-noise ratio at high linear densities.
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Micromagnetic Model Analysis of Planar-Type Write Head Field Response and Dependence on Pole Tip, Return Yoke, and Shield Structure
IEEE Transactions on Magnetics, 2013Co-Authors: Yasushi Kanai, Kiyoshi Yamakawa, Hidekazu Tamura, Kazuetsu Yoshida, Simon J. Greaves, Hiroaki MuraokaAbstract:We used a micromagnetic model to investigate the high-frequency (1-5 GHz) response, peak recording field strength, recording field gradient, and adjacent track erasure (ATE) field for various Main Pole tip, shield, and return yoke structures in planar type heads. The effect of the Pole tip area at the air-bearing surface (ABS) and the return yoke structure is also discussed. It was found that the Pole tip and shield arrangement had a major effect on the peak recording field strength, recording field gradient, and ATE field, i.e., the trailing and side shields work to reduce the undesired field, however, they also slow the head field response due to the interaction between the Main Pole tip and the shield. The field responses are also dependent on the Main Pole tip-shield structures and Pole tip structures. The return yoke thickness and area were important determinants of response speed and peak field.
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Requirements for soft magnetic underlayer (SUL)—Micromagnetic simulations of single-Pole-type write heads and SUL systems
Journal of Magnetism and Magnetic Materials, 2012Co-Authors: Yasushi Kanai, Simon John Greaves, Yoshihiro Jinbo, K. Yoshida, Kazuya Koyama, Hiroaki MuraokaAbstract:Abstract Landau–Lifshitz–Gilbert micromagnetic models were used to analyze the head field distributions and high-frequency responses for various soft magnetic underlayer thicknesses (t-SUL) and saturation magnetization flux densities (Bs) of single-Pole-type (SPT) head–SUL systems. It was found that Bs of 10–12 kG and t-SUL of 30–45 nm would be sufficient for the examined head and perhaps for most next generation head–SUL systems. Antiferromagnetic coupling in the SUL affects the head and SUL magnetization and, eventually, the head field. With regard to the head magnetization response, it was found that the magnetization under the coil responded first, while the response at the Main Pole tip was quite slow, even compared with the head field. The Main Pole tip of the head was fully saturated and the Main Pole yoke was almost saturated, while the SUL was not saturated in the examined head–SUL system.
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The feasibility of bit-patterned recording at 4 Tb/in.2 without heat-assist
Journal of Applied Physics, 2011Co-Authors: Simon John Greaves, Hiroaki Muraoka, Yasushi KanaiAbstract:Magnetic recording on bit patterned media with dot densities of 4 Tbit/in.2 was simulated. Head field distributions of shielded, single Pole write heads with various Main Pole widths were used for recording. Write windows, showing the range of head positions which resulted in error-free recording and no adjacent track erasure, were calculated. The bit aspect ratio (BAR) and magnetic spacing between the write head and the medium were varied and the system with the lowest write error rate was found to be a 1:1 BAR, shingled recording system. For single-track recording a 2:1 BAR and a magnetic spacing of 3.5 nm gave the lowest write-error rate.
Y Nakamura - One of the best experts on this subject based on the ideXlab platform.
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New high field single-Pole head design with an ultra-fine coil
Journal of Magnetism and Magnetic Materials, 2005Co-Authors: Kiyoshi Yamakawa, Hiroaki Muraoka, Kazuhiro Ouchi, Kazuyuki Ise, K. Sagae, Hajime Aoi, Y NakamuraAbstract:Abstract Improvement in head field of single-Pole heads was investigated in terms of coil design. From a simple analysis on hollow cylinder-shaped coil, a quite strong field was found to be created for the coil with inner diameter less than 100 nm. According to this result, a new single-Pole head having an ultra-fine coil at its Main-Pole tip was proposed. The field calculation with FEM showed the new head designed for 1 Tbit/in 2 exhibited a strong field larger than 30 kOe owing to enhancement of coil field. Furthermore, a sub-return yoke placed close to the Main Pole improved head field gradient.
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Recording field analysis of narrow-track SPT head with side shields, tapered Main Pole, and tapered return path for 1 Tb/in/sup 2/
IEEE Transactions on Magnetics, 2003Co-Authors: Yasushi Kanai, Hiroaki Muraoka, R. Matsubara, H. Watanabe, Y NakamuraAbstract:Results are presented for a three-dimensional finite-element method simulation of a head/medium model for 1 Tb/in/sup 2/ (540 ktpi with 38-nm track width and 47-nm track pitch, 1.8 Mbpi with minimum bit length of 11 nm). We have simultaneously introduced three new structures, side shields, tapered Main Pole, and tapered return path for the head in order to satisfy the requirement for a large recording field, small stray field to the adjacent tracks, and a field distribution that is robust for skew problems, which are all indispensable for higher linear and track density recording.
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Performance of PRML systems in perpendicular magnetic recording by a bi-layered Main-Pole head
Journal of Magnetism and Magnetic Materials, 1996Co-Authors: Y. Kurihara, Hiroaki Muraoka, Hisashi Osawa, Yoshihiro Okamoto, Y NakamuraAbstract:Abstract For perpendicular magnetic recording by a bi-layered Main-Pole head which shows an excellent linearity, the performance of PRML system combining partial response (PR) system with maximum likelihood (ML) decoding is studied. The bit-error rate of the PRML system using a PR(1,1,0,0,0,0, − 1, − 1) system is obtained by computer simulation and compared with that of the conventional PRML system. It is shown that our PRML system exhibits better performance than the conventional PRML system in high density recording.
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A Design Consideration for Main-Pole Shapes of Single-Pole Heads
IEEE Translation Journal on Magnetics in Japan, 1994Co-Authors: K. Takano, Y NakamuraAbstract:The magnetic field distribution of a single-Pole head in combination with a double-layered recording medium were analyzed by a two-dimensional finite element method. In the recording process, magnetic saturation occurs midway in the Main Pole, and this saturation decreases the head field strength and the sharpness. On the other hand, a large amount of magnetic flux leaks out from the middle of the Main Pole in reproduction. In accordance with these results, we designed a new Main Pole structure. As a result, the recording and readback sensitivities and the overwrite were improved. A D50 of 170 kFRPI was obtained by combining this new SPT head, with an 0.15 μm thick Main Pole, with a double-layered hard disk employing an 0.05 μm thick Co-Cr recording layer.
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Single-Pole Heads with Thin Fe-Si Main-Pole Films
IEEE Translation Journal on Magnetics in Japan, 1994Co-Authors: K. Takano, Y NakamuraAbstract:The linear recording density in perpendicular magnetic recording is limited by the thickness of the Main-Pole in the single-Pole head. In order to raise the practical readback resolution, a thin Main-Pole film is indispensable. Fe-Si film has a large saturation magnetization and good soft magnetic properties are obtained at thicknesses between 50 and 200 nm. However, as the film thickness decreases below 100 nm, the doMain wall structure and doMain configuration change from Bloch-type walls and closure doMains. A head with such a thin film as its Main-Pole has unstable readback output and poor resolution. The authors therefore adopted as the Main-Pole an Fe-Si/SiO 2 multi-layered film whose doMain structure differs from that of a single-layer Fe-Si film. As a result, the output stability and high-density response could be improved by controlling the intermediate layer (hereafter "inter-layer") thickness and the number of magnetic layers.
Kiyoshi Yamakawa - One of the best experts on this subject based on the ideXlab platform.
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Micromagnetic Model Analysis of Planar-Type Write Head Field Response and Dependence on Pole Tip, Return Yoke, and Shield Structure
IEEE Transactions on Magnetics, 2013Co-Authors: Yasushi Kanai, Kiyoshi Yamakawa, Hidekazu Tamura, Kazuetsu Yoshida, Simon J. Greaves, Hiroaki MuraokaAbstract:We used a micromagnetic model to investigate the high-frequency (1-5 GHz) response, peak recording field strength, recording field gradient, and adjacent track erasure (ATE) field for various Main Pole tip, shield, and return yoke structures in planar type heads. The effect of the Pole tip area at the air-bearing surface (ABS) and the return yoke structure is also discussed. It was found that the Pole tip and shield arrangement had a major effect on the peak recording field strength, recording field gradient, and ATE field, i.e., the trailing and side shields work to reduce the undesired field, however, they also slow the head field response due to the interaction between the Main Pole tip and the shield. The field responses are also dependent on the Main Pole tip-shield structures and Pole tip structures. The return yoke thickness and area were important determinants of response speed and peak field.
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Irradiation Damage in Fe-Co Thin Films With Low-Energy Ion Beam
IEEE Transactions on Magnetics, 2010Co-Authors: Yuichi Ohsawa, Kiyoshi Yamakawa, Hiroaki MuraokaAbstract:The authors estimated the effect of ion-beam irradiation damage on saturation magnetic flux density (B s) in Fe-Co thin films, a material expected to be used as a Main Pole in write heads in the era of Tbits/in2 recording density. Fe-Co thin film deposition and successive ion-beam irradiation at 250 eV and a capping layer deposition were performed in the same ion-beam etching apparatus without breaking vacuum. The etching tests revealed B s of the films with thickness of about 10 nm was decreased by the ion-beam irradiation; about 0.1-0.2 T decrease in B s was observed with several nanometers etching. Regardless of etching depth, about 0.1 T decrease in B s would appear even in the case of shallow etching of about 1 nm. Damage control in the Main Pole fabrication would be one of the important issues for the write heads.
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Effect of ion-beam etching damage in Fe-Co tapered Main Pole
Journal of Applied Physics, 2009Co-Authors: Yuichi Ohsawa, Kiyoshi Yamakawa, Hiroaki MuraokaAbstract:Effect of ion-beam etching damage in Fe–Co films was estimated and magnetic calculation of the planar head using tapered Main Pole (MP) including the etching damage was performed. The etching test on the Fe–Co films, whose thickness corresponds to half of the trackwidth for several Tbits/in.2, showed decrease in saturation magnetic flux density (Bs) and increase in coercivity with a 250 eV ion beam. The magnetic calculation showed relatively large decrease in head field and head field gradient as Bs of the damaged region decreases from 2.4 T. Damage control in the MP fabrication is one of the important issues for Tbits/in.2-era write heads.
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Pole design optimization of shielded planar writer for 2 Tbit/in2 recording
Journal of Applied Physics, 2009Co-Authors: Kiyoshi Yamakawa, Simon John Greaves, Yuichi Ohsawa, Hiroaki MuraokaAbstract:A shielded planar head with a multi-step-tapered Main Pole assuming ion-beam milling fabrication was studied to obtain a large recording field along with suppressed fringing field. The head Main Pole with a three-step-tapered structure was optimized in terms of the top, Main, and bottom slope angles. The optimized head showed a remarkably suppressed fringing field compared with a conventional single-step-tapered Pole head. The recording simulation suggests that the head has the potential for 2 Tbit/in2 recording in combination with a bit patterned medium.
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Writing Performance of a Planar Single-Pole Head With a Main Pole Fabricated by Ion-Beam Milling
IEEE Transactions on Magnetics, 2008Co-Authors: Yuichi Ohsawa, Kiyoshi Yamakawa, Hiroaki MuraokaAbstract:Writing performance of a shielded planar head with an ion-beam-fabricated Main Pole was estimated. Magnetic field simulation based on an ion-beam-etched Fe-Co film profile revealed that the two- or three-step-tapered Main Pole structure, which is one of characteristic configurations of the ion-beam process, has high writing and fabricating potential compared with that of the silicon template process. Especially, the three-step-tapered Main Pole shows not only high field strength (15 kOe) and field gradient (500 Oe/nm) but also well- suppressed fringing field. The shielded planar head with the ion-beam-milling-processed Main Pole is one of the leading candidates for application as a writer in the era of Tbpsi recording.
Yasushi Kanai - One of the best experts on this subject based on the ideXlab platform.
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micromagnetic model simulations considering write head spin torque oscillator and double layered medium altogether
IEEE Transactions on Magnetics, 2019Co-Authors: Yasushi Kanai, Simon John Greaves, Ryo Itagaki, H MuraokaAbstract:Micromagnetic model simulations were performed to investigate spin–torque oscillators (STOs) integrated into the Main Pole–trailing shield (MP–TS) gap of the write head (integrated STO). First, the oscillation states of a tilted STO were investigated in a model comprising the write head, STO, and medium soft underlayer (SUL). We found that inserting the STO into a non-parallel MP–TS gap resulted in more stable oscillation. Second, we performed full micromagnetic simulations of the write head, STO, SUL, and recording layer (RL), and the oscillation of the tilted STO was investigated. We found that the RL affected the STO oscillation to some extent; however, the effect was smaller than that from the write head. We also discuss the calculation times for various structures with and without the RL, and with/without medium motion.
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Micromagnetic model simulation of spin-torque oscillator and write head for microwave-assisted magnetic recording — Spin injection layer with in-plane anisotropy
2018 International Applied Computational Electromagnetics Society Symposium (ACES), 2018Co-Authors: Yasushi Kanai, Simon John Greaves, Ryo Itagaki, Hiroaki MuraokaAbstract:Micromagnetic simulations were carried out to obtain stable oscillation of a spin transfer torque oscillator (STO) inserted into the gap between the Main Pole and trailing shield of a write head. We assumed a spin injection layer with in-plane anisotropy. Results show that reducing the magnetostatic interaction between the write head and the STO is the key to obtaining stable STO oscillation.
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Microwave-Assisted Shingled Magnetic Recording
IEEE Transactions on Magnetics, 2015Co-Authors: Simon John Greaves, Yasushi Kanai, Hiroaki MuraokaAbstract:Simulations of shingled, microwave-assisted magnetic recording were carried out. First, a simplified model of the head field near the corner of the Main Pole of a write head was used to understand the effect of the spin torque oscillator (STO) position relative to the head. Next, shingled tracks were written and evaluated for two different write head and STO geometries. For shingled recording, locating a rotated STO on the side of the Main Pole may provide some advantages in that medium grains experience the high-frequency (HF) field for a longer time and the chirality of the HF field does not change as the grains pass by the STO. Recording simulations show that the rotated STO writes smoother track edges at lower densities, but there is little difference in signal-to-noise ratio at high linear densities.
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Micromagnetic Model Analysis of Planar-Type Write Head Field Response and Dependence on Pole Tip, Return Yoke, and Shield Structure
IEEE Transactions on Magnetics, 2013Co-Authors: Yasushi Kanai, Kiyoshi Yamakawa, Hidekazu Tamura, Kazuetsu Yoshida, Simon J. Greaves, Hiroaki MuraokaAbstract:We used a micromagnetic model to investigate the high-frequency (1-5 GHz) response, peak recording field strength, recording field gradient, and adjacent track erasure (ATE) field for various Main Pole tip, shield, and return yoke structures in planar type heads. The effect of the Pole tip area at the air-bearing surface (ABS) and the return yoke structure is also discussed. It was found that the Pole tip and shield arrangement had a major effect on the peak recording field strength, recording field gradient, and ATE field, i.e., the trailing and side shields work to reduce the undesired field, however, they also slow the head field response due to the interaction between the Main Pole tip and the shield. The field responses are also dependent on the Main Pole tip-shield structures and Pole tip structures. The return yoke thickness and area were important determinants of response speed and peak field.
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Requirements for soft magnetic underlayer (SUL)—Micromagnetic simulations of single-Pole-type write heads and SUL systems
Journal of Magnetism and Magnetic Materials, 2012Co-Authors: Yasushi Kanai, Simon John Greaves, Yoshihiro Jinbo, K. Yoshida, Kazuya Koyama, Hiroaki MuraokaAbstract:Abstract Landau–Lifshitz–Gilbert micromagnetic models were used to analyze the head field distributions and high-frequency responses for various soft magnetic underlayer thicknesses (t-SUL) and saturation magnetization flux densities (Bs) of single-Pole-type (SPT) head–SUL systems. It was found that Bs of 10–12 kG and t-SUL of 30–45 nm would be sufficient for the examined head and perhaps for most next generation head–SUL systems. Antiferromagnetic coupling in the SUL affects the head and SUL magnetization and, eventually, the head field. With regard to the head magnetization response, it was found that the magnetization under the coil responded first, while the response at the Main Pole tip was quite slow, even compared with the head field. The Main Pole tip of the head was fully saturated and the Main Pole yoke was almost saturated, while the SUL was not saturated in the examined head–SUL system.
Simon John Greaves - One of the best experts on this subject based on the ideXlab platform.
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micromagnetic model simulations considering write head spin torque oscillator and double layered medium altogether
IEEE Transactions on Magnetics, 2019Co-Authors: Yasushi Kanai, Simon John Greaves, Ryo Itagaki, H MuraokaAbstract:Micromagnetic model simulations were performed to investigate spin–torque oscillators (STOs) integrated into the Main Pole–trailing shield (MP–TS) gap of the write head (integrated STO). First, the oscillation states of a tilted STO were investigated in a model comprising the write head, STO, and medium soft underlayer (SUL). We found that inserting the STO into a non-parallel MP–TS gap resulted in more stable oscillation. Second, we performed full micromagnetic simulations of the write head, STO, SUL, and recording layer (RL), and the oscillation of the tilted STO was investigated. We found that the RL affected the STO oscillation to some extent; however, the effect was smaller than that from the write head. We also discuss the calculation times for various structures with and without the RL, and with/without medium motion.
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micromagnetic model analysis of spin torque oscillator sto integrated into recording write head for microwave assisted magnetic recording oscillation of sto vs rise time of in gap field
IEEE International Magnetics Conference, 2018Co-Authors: Y Kanai, Simon John Greaves, Ryo Itagaki, H MuraokaAbstract:Microwave-assisted magnetic recording (MAMR) [1] is one candidate for next-generation perpendicular magnetic recording [2]. Stable oscillation is one of the most important factors for spin-torque oscillators (STOs) used in a MAMR system. We performed micromagnetic simulations and found that stable STO oscillations were hard to obtain when the STO was inserted into the Main Pole - trailing shield (MP-TS) gap, primarily due to the strong magnetostatic interactions between the STO and write head [3]. We also showed that the rise time of the field applied to an isolated STO greatly affected the STO oscillation [4], i.e., a shorter rise time gave better, more consistent STO oscillation. In this paper, we show that the rise time of the in-gap field acting on the STO is critical to stable STO oscillation. We also show that the combination of a tilted STO and a tilted Main Pole - trailing shield gap results in stable STO oscillation due to weaker magnetostatic interactions between the STO and write head. Calculation Model A micromagnetic model analysis was carried out considering a double-layered STO utilizing transmission spin torque. We used commercial micromagnetic software (Fujitsu, EXAMAG v.2.1) [5]. The thickness of the field generation layer (FGL) was 10 nm, whilst the spin injection layer (SIL) was 2 nm thick. A 2 nm thick, non-magnetic inter layer was located between the FGL and SIL. The saturation magnetization $(4 \pi M_{s})$ was 20 kG for the FGL and 6 kG for the SIL. The anisotropy fields $(H_{k})$ of both the FGL and SIL were 31.4 Oe. The exchange constants, A, were $2.5 \times 10 ^{-6}$ erg/cm3 for the FGL and $0.75 \times 10 ^{-6}$ erg/cm3 for the SIL. The Gilbert damping factor, $\alpha $, was 0.02 for both the FGL and SIL. The write head model had overall dimensions close to those of commercial write heads $(3.25 \mu \mathrm {m}\times 2.55 \mu \mathrm {m}\times 4.5 \mu \mathrm {m})$.
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Micromagnetic model simulation of spin-torque oscillator and write head for microwave-assisted magnetic recording — Spin injection layer with in-plane anisotropy
2018 International Applied Computational Electromagnetics Society Symposium (ACES), 2018Co-Authors: Yasushi Kanai, Simon John Greaves, Ryo Itagaki, Hiroaki MuraokaAbstract:Micromagnetic simulations were carried out to obtain stable oscillation of a spin transfer torque oscillator (STO) inserted into the gap between the Main Pole and trailing shield of a write head. We assumed a spin injection layer with in-plane anisotropy. Results show that reducing the magnetostatic interaction between the write head and the STO is the key to obtaining stable STO oscillation.
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Microwave-Assisted Shingled Magnetic Recording
IEEE Transactions on Magnetics, 2015Co-Authors: Simon John Greaves, Yasushi Kanai, Hiroaki MuraokaAbstract:Simulations of shingled, microwave-assisted magnetic recording were carried out. First, a simplified model of the head field near the corner of the Main Pole of a write head was used to understand the effect of the spin torque oscillator (STO) position relative to the head. Next, shingled tracks were written and evaluated for two different write head and STO geometries. For shingled recording, locating a rotated STO on the side of the Main Pole may provide some advantages in that medium grains experience the high-frequency (HF) field for a longer time and the chirality of the HF field does not change as the grains pass by the STO. Recording simulations show that the rotated STO writes smoother track edges at lower densities, but there is little difference in signal-to-noise ratio at high linear densities.
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Requirements for soft magnetic underlayer (SUL)—Micromagnetic simulations of single-Pole-type write heads and SUL systems
Journal of Magnetism and Magnetic Materials, 2012Co-Authors: Yasushi Kanai, Simon John Greaves, Yoshihiro Jinbo, K. Yoshida, Kazuya Koyama, Hiroaki MuraokaAbstract:Abstract Landau–Lifshitz–Gilbert micromagnetic models were used to analyze the head field distributions and high-frequency responses for various soft magnetic underlayer thicknesses (t-SUL) and saturation magnetization flux densities (Bs) of single-Pole-type (SPT) head–SUL systems. It was found that Bs of 10–12 kG and t-SUL of 30–45 nm would be sufficient for the examined head and perhaps for most next generation head–SUL systems. Antiferromagnetic coupling in the SUL affects the head and SUL magnetization and, eventually, the head field. With regard to the head magnetization response, it was found that the magnetization under the coil responded first, while the response at the Main Pole tip was quite slow, even compared with the head field. The Main Pole tip of the head was fully saturated and the Main Pole yoke was almost saturated, while the SUL was not saturated in the examined head–SUL system.
