Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177048
S. Sankaranarayanan, E. Kurtas, B. Vasic
Cheng (Doctoral Dissertation, CIT, Pasadena, California, 1997) introduced a class of linear codes called low-density generator matrix (LDGM) codes and studied its performance on a memoryless additive white Gaussian noise (AWGN) channel. In this paper, we study its performance on perpendicular magnetic recording channels. The results shown in this paper indicate that the bit-error rate (BER) performance of some LDGM-codes is comparable to that of low-density parity check (LDPC) codes of the same rate.
{"title":"Performance of low-density generator matrix codes on perpendicular recording channels","authors":"S. Sankaranarayanan, E. Kurtas, B. Vasic","doi":"10.1109/NAPMRC.2003.1177048","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177048","url":null,"abstract":"Cheng (Doctoral Dissertation, CIT, Pasadena, California, 1997) introduced a class of linear codes called low-density generator matrix (LDGM) codes and studied its performance on a memoryless additive white Gaussian noise (AWGN) channel. In this paper, we study its performance on perpendicular magnetic recording channels. The results shown in this paper indicate that the bit-error rate (BER) performance of some LDGM-codes is comparable to that of low-density parity check (LDPC) codes of the same rate.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131263485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177012
H. Sawaguchi, Y. Nishida, T. Nakagawa, H. Takano, H. Aoi
Non-stationary media noise is one of the major disturbances that occur in higher density perpendicular magnetic recording channels. The strongly signal-dependent and correlated statistical nature of this noise means that it significantly worsens error-rates of traditional partial-response maximum likelihood (PRML) data-detection. As densities of recording become increasingly high, thermal stability issues place serious restrictions on the use of smaller grained recording media to reduce the media noise. To mitigate requirements for the noise reduction, we have introduced a sub-optimal ML detection scheme for media-noise-dominant channels. This scheme is based on the estimation of signal-dependent correlation-sensitive (SDCS) metric for soft-output postprocessing detection. By focusing on correcting only a few most-likely error-events in PRML detection, this media-noise soft-output detection scheme provides a good tradeoff between detection performance and computational complexity.
{"title":"Signal processing and coding techniques for perpendicular recording","authors":"H. Sawaguchi, Y. Nishida, T. Nakagawa, H. Takano, H. Aoi","doi":"10.1109/NAPMRC.2003.1177012","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177012","url":null,"abstract":"Non-stationary media noise is one of the major disturbances that occur in higher density perpendicular magnetic recording channels. The strongly signal-dependent and correlated statistical nature of this noise means that it significantly worsens error-rates of traditional partial-response maximum likelihood (PRML) data-detection. As densities of recording become increasingly high, thermal stability issues place serious restrictions on the use of smaller grained recording media to reduce the media noise. To mitigate requirements for the noise reduction, we have introduced a sub-optimal ML detection scheme for media-noise-dominant channels. This scheme is based on the estimation of signal-dependent correlation-sensitive (SDCS) metric for soft-output postprocessing detection. By focusing on correcting only a few most-likely error-events in PRML detection, this media-noise soft-output detection scheme provides a good tradeoff between detection performance and computational complexity.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132486345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177021
Y. Ikeda, N. Supper, K. Takano, H. Do
Perpendicular recording is the most promising candidate to achieve areal densities exceeding 1 Tbit/in/sup 2/. To achieve this goal, small grains with high uniaxial anisotropy and good magnetic isolation are required for the media. However, the optimum exchange coupling is also necessary to reduce DC-erase noise caused by the reversed grains due to the high demagnetization field. The high nucleation field H/sub n/, and the low noise of the CoPtCrO perpendicular medium are attractive features. In this paper, the medium noise and exchange coupling correlation has been investigated by changing the oxygen ratio in the sputter gas.
{"title":"Inter-granular exchange coupling control by oxygen ratio in CoPtCrO perpendicular media","authors":"Y. Ikeda, N. Supper, K. Takano, H. Do","doi":"10.1109/NAPMRC.2003.1177021","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177021","url":null,"abstract":"Perpendicular recording is the most promising candidate to achieve areal densities exceeding 1 Tbit/in/sup 2/. To achieve this goal, small grains with high uniaxial anisotropy and good magnetic isolation are required for the media. However, the optimum exchange coupling is also necessary to reduce DC-erase noise caused by the reversed grains due to the high demagnetization field. The high nucleation field H/sub n/, and the low noise of the CoPtCrO perpendicular medium are attractive features. In this paper, the medium noise and exchange coupling correlation has been investigated by changing the oxygen ratio in the sputter gas.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":" 15","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132074326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177028
J. Ariake, H. Yamane, N. Honda, K. Ouchi
Intermediate layers for perpendicular magnetic recording media have been studied for controlling storage layers with fine grains. The magnetic properties of the media was investigated for understanding the effect of the intermediate layer. H/sub c/spl perp// for the medium with the Pt/C intermediate layer showed a little bit large value compared with that with the Pt/Ti one. TEM images of the media were investigated. We show that platinum and carbon layers are suitable intermediate layers for a very fine Co-Cr-Pt-Nb storage layer in double layered perpendicular magnetic recording media.
{"title":"Pt/C intermediate layer for Co-Cr perpendicular magnetic recording media with extremely high linear density","authors":"J. Ariake, H. Yamane, N. Honda, K. Ouchi","doi":"10.1109/NAPMRC.2003.1177028","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177028","url":null,"abstract":"Intermediate layers for perpendicular magnetic recording media have been studied for controlling storage layers with fine grains. The magnetic properties of the media was investigated for understanding the effect of the intermediate layer. H/sub c/spl perp// for the medium with the Pt/C intermediate layer showed a little bit large value compared with that with the Pt/Ti one. TEM images of the media were investigated. We show that platinum and carbon layers are suitable intermediate layers for a very fine Co-Cr-Pt-Nb storage layer in double layered perpendicular magnetic recording media.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129176478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177049
Y. Hirayama, I. Tamai, I. Takekuma, Y. Nishida, Y. Hosoe
CoCr-alloy perpendicular magnetic recording media have been investigated, as the Cr segregated structure in the CoCr-alloy recording layer is suitable for obtaining low noise properties. Recently, the grain size of the recording layer is required to be very small for high-density recording, therefore the thermal stability of the recorded bit is becoming a critical issue. The magnetic anisotropy should be improved to keep the thermal stability of the recording layer which consists of small grains. The addition of the Pt element and a decrease of Cr content are required in the CoCr-alloy. This, however, results in higher medium noise due to increasing inter-granular exchange coupling. In this paper, the effects of Cr content on the magnetic and recording properties in post-annealed CoCrPt-alloy perpendicular media were investigated. The post-annealing treatment is expected to enhance Cr diffusion into the CoCrPt grain boundary from a nonmagnetic CoCr intermediate layer.
{"title":"CoCrPt-alloy perpendicular media for high-density magnetic recording","authors":"Y. Hirayama, I. Tamai, I. Takekuma, Y. Nishida, Y. Hosoe","doi":"10.1109/NAPMRC.2003.1177049","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177049","url":null,"abstract":"CoCr-alloy perpendicular magnetic recording media have been investigated, as the Cr segregated structure in the CoCr-alloy recording layer is suitable for obtaining low noise properties. Recently, the grain size of the recording layer is required to be very small for high-density recording, therefore the thermal stability of the recorded bit is becoming a critical issue. The magnetic anisotropy should be improved to keep the thermal stability of the recording layer which consists of small grains. The addition of the Pt element and a decrease of Cr content are required in the CoCr-alloy. This, however, results in higher medium noise due to increasing inter-granular exchange coupling. In this paper, the effects of Cr content on the magnetic and recording properties in post-annealed CoCrPt-alloy perpendicular media were investigated. The post-annealing treatment is expected to enhance Cr diffusion into the CoCrPt grain boundary from a nonmagnetic CoCr intermediate layer.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"130 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114761753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177043
K. Gao, H. Bertram
Tilted and conventional perpendicular recording has been proposed as an effective method for recording densities beyond 100 Gbit/in/sup 2/. Recent study have shown the recording densities were limited, to large extend, by the anisotropy magnitude distribution In this paper, we study the effects of distributions in detail utilizing both analyses and micromagnetic simulations.
{"title":"Effects of distributions in tilted and conventional perpendicular recording","authors":"K. Gao, H. Bertram","doi":"10.1109/NAPMRC.2003.1177043","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177043","url":null,"abstract":"Tilted and conventional perpendicular recording has been proposed as an effective method for recording densities beyond 100 Gbit/in/sup 2/. Recent study have shown the recording densities were limited, to large extend, by the anisotropy magnitude distribution In this paper, we study the effects of distributions in detail utilizing both analyses and micromagnetic simulations.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125903505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177029
K. Shintaku, K. Yamakawa, K. Ouchi
Fe-Co based films have been investigated for writing head core materials with a high B/sub s/ in recent years. We have reported that the combination of a small amount of Al/sub 2/O/sub 3/ addition and a soft magnetic underlayer film is important to obtain small H/sub ch/ with high B/sub s/ of 2.4 T in a wide range of film thickness for Fe-Co films. The mechanism of soft magnetic properties by using the Al/sub 2/O/sub 3/ addition and/or the soft magnetic underlayer film is studied. We confirm that the soft magnetic properties of Fe-Co system films are related to the expansion of the lattice constant and random crystal orientation.
{"title":"Soft magnetic properties and structure of high B/sub s/ Fe-Co-Al-O films","authors":"K. Shintaku, K. Yamakawa, K. Ouchi","doi":"10.1109/NAPMRC.2003.1177029","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177029","url":null,"abstract":"Fe-Co based films have been investigated for writing head core materials with a high B/sub s/ in recent years. We have reported that the combination of a small amount of Al/sub 2/O/sub 3/ addition and a soft magnetic underlayer film is important to obtain small H/sub ch/ with high B/sub s/ of 2.4 T in a wide range of film thickness for Fe-Co films. The mechanism of soft magnetic properties by using the Al/sub 2/O/sub 3/ addition and/or the soft magnetic underlayer film is studied. We confirm that the soft magnetic properties of Fe-Co system films are related to the expansion of the lattice constant and random crystal orientation.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"134 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133458552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177063
K. Nakamoto, Y. Kawato, N. Yoshida, Y. Okada, M. Hatatani, M. Mochizuki, K. Watanabe, M. Fuyama
Perpendicular recording with sufficient thermal stability has great potential for next-generation recording with areal densities over 100 Gb/in/sup 2/. One of the biggest problems for single-pole writers is head-induced erasure, such as erase-after-write This erasure is due to the high remanent magnetization of the main pole. We fabricated single-pole writers with a domain stabilization technique to reduce the remanence, and highly sensitive tunneling magnetoresistive (TMR) readers for 100 Gb/in/sup 2/ perpendicular recording.
{"title":"Perpendicular recording heads for areal densities over 100 Gb/in/sup 2/","authors":"K. Nakamoto, Y. Kawato, N. Yoshida, Y. Okada, M. Hatatani, M. Mochizuki, K. Watanabe, M. Fuyama","doi":"10.1109/NAPMRC.2003.1177063","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177063","url":null,"abstract":"Perpendicular recording with sufficient thermal stability has great potential for next-generation recording with areal densities over 100 Gb/in/sup 2/. One of the biggest problems for single-pole writers is head-induced erasure, such as erase-after-write This erasure is due to the high remanent magnetization of the main pole. We fabricated single-pole writers with a domain stabilization technique to reduce the remanence, and highly sensitive tunneling magnetoresistive (TMR) readers for 100 Gb/in/sup 2/ perpendicular recording.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132438249","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177036
B. Lengsfield, M. Schabes
This work extends earlier theoretical studies as the time dependent fields present at a transition during the recording process were analyzed as a function of magnetic spacing, exchange, saturation magnetization and anisotropy. The trade-off between smaller transition lengths and larger cross track correlation lengths as function of these media parameters was investigated for a large matrix of material parameters. The simulated signal roll off produced in this study was found to agree closely with recent experimental studies of high performance granular media. Our simulations indicate that there is a range of material parameters that produces a small transition length in thermally stable perpendicular media.
{"title":"Optimization of the performance of perpendicular magnetic recording media","authors":"B. Lengsfield, M. Schabes","doi":"10.1109/NAPMRC.2003.1177036","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177036","url":null,"abstract":"This work extends earlier theoretical studies as the time dependent fields present at a transition during the recording process were analyzed as a function of magnetic spacing, exchange, saturation magnetization and anisotropy. The trade-off between smaller transition lengths and larger cross track correlation lengths as function of these media parameters was investigated for a large matrix of material parameters. The simulated signal roll off produced in this study was found to agree closely with recent experimental studies of high performance granular media. Our simulations indicate that there is a range of material parameters that produces a small transition length in thermally stable perpendicular media.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121812763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2003-01-06DOI: 10.1109/NAPMRC.2003.1177059
R.J.M.V. de Veerdonk, Xiaowei Wu, G. Ju
We present experimental results for a series of perpendicular recording media samples, using magnetometry methods adopted for the perpendicular geometry. The inadequacy of characterization using only hysteresis loops is demonstrated, as well as the influence of a demagnetization field and its importance for the interpretation of the results. By using the more involved and time-consuming measurements described in this work, some of the relevant materials properties can be determined and serve as inputs for advanced micromagnetic recording models.
{"title":"Experimental characterization methods for perpendicular recording materials","authors":"R.J.M.V. de Veerdonk, Xiaowei Wu, G. Ju","doi":"10.1109/NAPMRC.2003.1177059","DOIUrl":"https://doi.org/10.1109/NAPMRC.2003.1177059","url":null,"abstract":"We present experimental results for a series of perpendicular recording media samples, using magnetometry methods adopted for the perpendicular geometry. The inadequacy of characterization using only hysteresis loops is demonstrated, as well as the influence of a demagnetization field and its importance for the interpretation of the results. By using the more involved and time-consuming measurements described in this work, some of the relevant materials properties can be determined and serve as inputs for advanced micromagnetic recording models.","PeriodicalId":111090,"journal":{"name":"Joint NAPMRC 2003. Digest of Technical Papers","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2003-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123905658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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