Milestone-Proposal:Perpendicular Magnetic Recording

From IEEE Milestones Wiki
Revision as of 03:55, 29 October 2020 by Yoichiro Tanaka (talk | contribs)


To see comments, or add a comment to this discussion, click here.

Docket #:2020-08

This Proposal has been approved, and is now a Milestone


To the proposer’s knowledge, is this achievement subject to litigation? No

Is the achievement you are proposing more than 25 years old? Yes

Is the achievement you are proposing within IEEE’s designated fields as defined by IEEE Bylaw I-104.11, namely: Engineering, Computer Sciences and Information Technology, Physical Sciences, Biological and Medical Sciences, Mathematics, Technical Communications, Education, Management, and Law and Policy. Yes

Did the achievement provide a meaningful benefit for humanity? Yes

Was it of at least regional importance? Yes

Has an IEEE Organizational Unit agreed to pay for the milestone plaque(s)? Yes

Has an IEEE Organizational Unit agreed to arrange the dedication ceremony? Yes

Has the IEEE Section in which the milestone is located agreed to take responsibility for the plaque after it is dedicated? Yes

Has the owner of the site agreed to have it designated as an IEEE Milestone? Yes


Year or range of years in which the achievement occurred:

1977

Title of the proposed milestone:

Perpendicular magnetic recording, 1977

Plaque citation summarizing the achievement and its significance:

In 1977, perpendicular magnetic recording was invented by Professor Shun-ichi Iwasaki of Tohoku University. The development of perpendicular recording medium and single pole head made the most of magnetic physics to realize the significant high-density recording performance. Since the first commercialization of perpendicular magnetic recording hard disk drives in 2005, the data storage technology by perpendicular magnetic recording has established the foundation of “big data” information society.

200-250 word abstract describing the significance of the technical achievement being proposed, the person(s) involved, historical context, humanitarian and social impact, as well as any possible controversies the advocate might need to review.


IEEE technical societies and technical councils within whose fields of interest the Milestone proposal resides.


In what IEEE section(s) does it reside?

IEEE Sendai Section

IEEE Organizational Unit(s) which have agreed to sponsor the Milestone:

IEEE Organizational Unit(s) paying for milestone plaque(s):

Unit: IEEE Sendai Section
Senior Officer Name: Hiroshi Kikuchi

IEEE Organizational Unit(s) arranging the dedication ceremony:

Unit: IEEE Sendai Section
Senior Officer Name: Professor Yoichiro Tanaka

IEEE section(s) monitoring the plaque(s):

IEEE Section: IEEE Sendai Section
IEEE Section Chair name: Motoyuki Sato

Milestone proposer(s):

Proposer name: Professor Yoichiro Tanaka
Proposer email: Proposer's email masked to public

Please note: your email address and contact information will be masked on the website for privacy reasons. Only IEEE History Center Staff will be able to view the email address.

Street address(es) and GPS coordinates in decimal form of the intended milestone plaque site(s):

Tohoku University Archives, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan GPS coordinates Latitude: 38.253458, Longitude: 140.873355.

Describe briefly the intended site(s) of the milestone plaque(s). The intended site(s) must have a direct connection with the achievement (e.g. where developed, invented, tested, demonstrated, installed, or operated, etc.). A museum where a device or example of the technology is displayed, or the university where the inventor studied, are not, in themselves, sufficient connection for a milestone plaque.

Please give the address(es) of the plaque site(s) (GPS coordinates if you have them). Also please give the details of the mounting, i.e. on the outside of the building, in the ground floor entrance hall, on a plinth on the grounds, etc. If visitors to the plaque site will need to go through security, or make an appointment, please give the contact information visitors will need. Tohoku University Archives is located on Tohoku University Katahira Campus where the research led to the invention of the Perpendicular Magnetic Recording in 1977 at the Research Institute of Electrical Communication. The plaque will be mounted on the wall of the Tohoku University Archives.

Are the original buildings extant?

Yes

Details of the plaque mounting:

The mounting will be on the wall of the Tohoku University Archives.

How is the site protected/secured, and in what ways is it accessible to the public?

The plaque will be protected with other valuable historical materials by the office of Tohoku University Archives. Public visitors can visit Tohoku University Archives during daytime hours on weekdays. Visitors have to show an ID card issued by the office in the building.

Who is the present owner of the site(s)?

Tohoku University

What is the historical significance of the work (its technological, scientific, or social importance)? If personal names are included in citation, include justification here. (see section 6 of Milestone Guidelines)

The most important significance is that perpendicular magnetic recording (PMR) opened a new paradigm of high areal density magnetic recording. PMR is the original invention by Professor Dr. Shun-ichi Iwasaki, Tohoku University, Sendai, Japan, in 1977 [1]. It is one of the most fundamental innovations in magnetic recording history, which has attained large-capacity storage technology which is indispensable for the present “big data” society. The significance of PMR is recognized as scientific, industrial, and social aspects.

Innovation of high density magnetic recording

    PMR achieved high areal density recording by the new recording scheme to align the recorded magnetization perpendicular to medium surface. Prior to PMR in longitudinal magnetic recording, recorded magnetization was formed in-plain, or parallel to the surface. The contrast is schematically shown in Fig. 1, where bit length corresponds to the length of each magnetization, or magnet, bearing one bit. In low densities, recorded longitudinal magnetization is stable, because demagnetization field in the elongated magnetization is small. In contrast, in high densities, short bit length induces large demagnetization field in the recorded bits that weakens the recorded magnetization. To avoid this difficulty, the recording medium should become thin, but in the case, the small bit volume made readout flux extremely too small to detect the data without read-errors. PMR fundamentally changed this situation by changing the direction of the recorded magnetization. As indicated in the figure, the anti-parallel magnetization is formed in PMR, which reduces demagnetization field in short bit lengths, or high linear densities. The first scientific significance is to realize this complementary nature of magneto-static energy in the recording medium [5]. Because of the superior high density performance, PMR was recognized as the next generation disk technology even in 1980s [6].

Fig1.gif

    Three key devices were newly developed to realize PMR: discovery of a cobalt-chrome (Co-Cr) thin film [3], development of a perpendicular writing head that generated a dominant perpendicular field referred to as shingle-pole head in 1978 [2], invention of a double-layer medium, which significantly enhanced head field strength [4]. Fig. 2 schematically indicates the combination of heads and medium structure of PMR (right) in comparison with those of longitudinal recording (left). In order to construct the high areal density PMR, both Co-Cr perpendicular anisotropy medium and single-pole writing head with the soft magnetic underlayer are indispensable. It should be stressed that, without the perpendicular anisotropy medium, stable perpendicular magnetization cannot be maintained, as widely recognized [7]. Fig. 3 shows magnetic characteristics, hysteresis loops, of the Co-Cr films developed in 1978 [3]. The square solid curves for perpendicularly applied field indicated strong perpendicular anisotropy, while the thin loops for in-plain field demonstrated good perpendicular orientation. Single-pole head generates the dominant perpendicular field that penetrates the medium. The soft-magnetic underlayer of the medium enhances the writing field strength and gradient by the magnetic image effect. Fig. 4 shows an early single-pole head developed for the measurements for tape recording experiments in late 1970s. These medium and head developed in the early stage were used to study the fundamental performance of PMR. The experimental setup of write and read operation with a perpendicular flexible disk and a single pole head was accomplished, as shown in Fig. 5. Spin-stand testing, which is a kind of practical experiments, was carried out with Co-Cr flexible disk and single-pole head before 1980.

Fig2.gif Fig3.gif Fig4.gif Fig5.gif

    In high areal density recording, another physical difficulty appeared in longitudinal recording, which was the thermal stability limit. Thermal energy of room temperature randomly disturbs the recoded magnetization, which causes probabilistic magnetization reversal. Because of the random reversals, the recorded information may randomly disappear, and therefore, it “forgets” the recorded information. The thermal stability is governed by the ratio of magnetic energy and thermal energy. The magnetic energy is defined as the product of magnetic anisotropy energy and bit volume. This is the reason why thermal agitation is severer in higher areal densities, or smaller bit volumes. PMR can employ a thick medium, in which bit volume can be much larger than longitudinal recording. Strong writing field of single pole head with the soft magnetic underlayer allows to employ a large anisotropy medium. PMR thus largely extends the physical limit by the thermal disturbance. So far, the superior areal density capability of PMR achieved almost tenfold greater density in experiments. The countermeasure of thermal stability limit is another important significance.
    Developments of new recording technologies are ongoing to achieve further high areal densities for next generation. It is clear that the direction of recorded magnetization is all perpendicular without exception. PMR is the basic technology even for the future recording. 

Industrial significance

    Because of the large production volume of HDD, PMR’s industrial impact is significant. Magnetic recording industry has had a great interest in PMR right after the first paper publication in 1977. During 1980s intensive research and development by magnetic recording industry were keenly carried out as joint research organized by Prof. Iwasaki [12]. Although there was a long halt during 1990s, the industry resumed the development around 2000. A prototype of a PMR hard disk drive (HDD) was demonstrated in IEEE Intermag conference 2000 by Hitachi Ltd and Tohoku University [8], [9]. Eventually a 1.8-inch hard disk drive for portable music player was commercialized in 2005 by Toshiba Corp followed by Hitachi and Seagate Technology, and others [10], [11], [14]. By 2010, all hard disk drive production with conventional recording had been replaced by PMR. Fig. 6 shows the shipment of hard disk drives [12]. Worldwide shipment of PMR hard disk drives has reached 600 million units in 2013 brought a big revenue to the industry. Thus, PMR had a big impact for industries with the vast shipment of the hard disk drives and related products.

Fig6.gif

    PMR has also encouraged spin-off effect of industrial applications for other technologies. All reading heads for PMR HDD were giant magneto-resistive heads, which based on spintronics. Individual HDD equipped several reading heads, which provides the largest application market for the spintronics technology. Besides, the large information storage capacity by PMR has pushed ahead with market growth of information technology (IT), such as cloud storage and large-scale data centers where vast amount of HDDs is used. The market size of this segment is huge, for which PMR contributes to the “big data” storage technology.

Contribution to IT technology and information society

    For audio/video and computers such as home electronics applications, medical equipment, automobile applications are unavoidable segments, but more significant application is big-data information storage technologies [12], [13], as shown in Fig. 7. Especially in the recent information society, amount of generated information is extremely large and rapidly increasing, approximately twofold every two years [13]. The worldwide amount of generated digital information becomes a gigantic amount of 16 zetta bytes in 2017 [13]. This tremendous growth of “big data” causes the strong demand of large capacity information storage for data centers, cloud computing, and information servers. HDD is widely used as the dominant storage device in networks and computers to store most of information. As commonly recognized high areal density capability achieved by PMR is an indispensable means for the big data. Areal density on a disk is the most crucial figure of merit in such applications. Innovation of PMR has dramatically increased storage capacity of HDD for personal computers and data servers. Both have satisfied the big demand of large storage capacity along with inexpensive bit cost. PMR thus accelerated development of storage technologies for modern information technology, which is another industrial significance to open the novel big data technology for next-generation information society.

Fig7.gif Fig8.gif

Honors and Awards

    The significance of this work can also be measured by the honors that have been given to Prof. Iwasaki directly in recognition of the outstanding technological contribution of PMR. In chronological order, he received IEEE Fellow (1984), Japan Academy Prize (1987), IEEE Cledo Brunetti Award (1989), IEEE Magnetics Society Achievement Award (2002), Admission of the Japan Academy (2003), Japan Prize (2010), Benjamin Franklin Medal (2014), and The Order of Cultural Merit (2013). They are all awarded to the outstanding contributions not only for the engineering achievement, but also significant impact to the social activities.

What obstacles (technical, political, geographic) needed to be overcome?

The most significant obstacle that had to be overcome was the deep gap between scientific accomplishment and industrial success [12]. After the success of the first experimental demonstration and the first paper publication in 1977, but the commercialization of PMR was 28 years later in 2005. It took long time to be brought to the market. PMR actually encountered the “death valley” during 1990s.

    The major reason was competition with conventional longitudinal recording. Areal density growth of conventional recording continued even in 1990s. Many technical difficulties showed up to record extremely small bits and to read information from the tiny magnetization, but highly sensitive read heads and new signal processing technique made longitudinal recording survive longer. Industries tend to stick to the conventional technology, unless it cannot satisfy required performance. However, a new brick wall obstructed the way after the year of 2000. The thermal stability limit blocked the areal density growth of longitudinal magnetic recording. Although PMR had to wait until 2005, it eventually became the front runner. A Japanese major newspaper reported the commercialization of PMR on May 21, 2005, as shown in Fig. 8 and its translation as ref. [11]. The heading reads “Perpendicular recording is commercialized. Tenfold capacity possible. Thirty-year-long research for hard disk technology from Japan.”. 
    The second reason was the big technology leap for the innovative development of PMR. Whole recording devices, e.g. heads, media, and signal processing, needed to be newly developed in order to be industrialized. The medium was totally changed from conventional iron-oxide longitudinal medium to Co-Cr based thin film perpendicular medium. Because perpendicular anisotropy medium firstly employed in PMR, time-consuming careful studies on magnetic characteristics, microstructure, and reliability were indispensable to develop practical disks for PMR. The same situation of single-pole head, which had to be newly developed to replace conventional ring head. It started from the head for tape recording as shown in Fig. 4, it finally demonstrated as a flying head for HDD fabricated by thin-film technology, as shown in ref [9]. There was fundamental structural change. Besides, fundamental recording theorem of PMR was established in that period.

What features set this work apart from similar achievements?

In longitudinal recording, areal density growth was attained according to the design concept of “scaling rule”. In order to attain high areal density recording, bit length and track width of recorded magnetization should be proportionally scaled down. The scaling rule tells that all related parameters should be proportionally reduced in order to maintain the aspect ratio of the recorded bits, for example, the thickness of medium, head to medium separation (or magnetic spacing), writing head field gradient, and reading head resolution. As previously mentioned, the demagnetization field of perpendicular and conventional longitudinal magnetization are contrastive, in longitudinal recording short bit length magnetization induce large demagnetizing field that tends to weaken the magnetization. The scaling rule therefore suggested a flat and small bit keeping the same aspect ratio of bit length to medium thickness. This scaling design rule, however, has an in evitable drawback, which brought deterioration of magnetic moments per bit due to the reduction of the total bit volume. This was the reason why conventional longitudinal magnetic recording required a very sensitive reading head, such as giant magneto-resistive head. PMR was the first accomplishment, which did not obey the scaling rule by using perpendicular magnetization to the medium surface.

    The next unavoidable physical limit showed up when the areal density was beyond the “thermal stability” limit. Any recorded magnetization cannot avoid the disturbance of room temperature. Recorded magnetization suffers from random fluctuation, which accidentally causes grain magnetization switching. To resist the thermal stability individual recorded bit need to have a sufficient magnetic energy that is proportional to volume. Obviously the scaling rule cannot prevent the reduction of the volume. The principle of complementarity between longitudinal and perpendicular magnetic recording made a breakthrough of the dilemma. For example, it says that thickness of the perpendicular magnetic recording can be thick to decrease the demagnetizing field. The magnetic energy of a bit, KuV, where Ku and V are anisotropy energy and bit volume, of the perpendicular recording medium can be larger than the thin longitudinal recording medium.
    After introducing the market, perpendicular magnetic recording achieved tenfold areal density growth in comparison with the maximum areal density by past longitudinal recording. Such large areal density is the essential significance of PMR.

Supporting texts and citations to establish the dates, location, and importance of the achievement: Minimum of five (5), but as many as needed to support the milestone, such as patents, contemporary newspaper articles, journal articles, or chapters in scholarly books. 'Scholarly' is defined as peer-reviewed, with references, and published. You must supply the texts or excerpts themselves, not just the references. At least one of the references must be from a scholarly book or journal article. All supporting materials must be in English, or accompanied by an English translation.

The following references have been uploaded as PDFs. The reference number is at the front of the file name.

[1]. Shun-ichi Iwasaki and Yoshihisa Nakamura, “An Analysis for the magnetization mode for high density magnetic recording,” IEEE Trans. Magn., vol. MAG-13, no. 5, pp. 1272-1277, Sep. 1977.

[2]. Shun-ichi Iwasaki and Yoshihisa Nakamura, “The magnetic field distribution of a perpendicular recording head,” IEEE Trans. Magn., vol. MAG-14, no. 5, pp. 436-438, Sep. 1978.

[3]. Shun-ichi Iwasaki and Kazuhiro Ouchi, “Co-Cr recording films with perpendicular magnetic anisotropy,” IEEE Trans. Magn., vol. MAG-14, no. 5, pp. 849-851, Sep. 1978.

[4]. Shun-ichi Iwasaki, Yoshihisa Nakamura, and Kazuhiro Ouchi, “Perpendicular magnetic recording with a composite anisotropy film,” IEEE Trans. Magn., vol. MAG-15, no. 6, pp. 1456-1458, Nov. 1979.

[5]. Shun-ichi Iwasaki, “Perpendicular magnetic recording,” IEEE Trans. Magn., vol. MAG-16, no. 1, pp.71-76, Jan. 1980.

[6]. C. S. Chi, “Higher density for disk memories,” IEEE Spectrum, p. 39, March 1981.

[7]. C. Denis Mee and Eric. D. Daniel, “Magnetic Recording Volume I Technology” McGraw Hill, p. 19, 1987. (early attempt failed. Situation changed by CoCr media)

[8]. Hisashi Takano, Yasutaka Nishida, Masaaki Futamoto, Hajime Aoi, Yoshihisa Nakamura, “Possibilities of 40 Gb/in2 perpendicular recording,” Digest of the 2000 IEEE International Magnetics Conference, AD-06, Apr. 2000.

[9]. Hisashi Takano, Yasutaka Nishida, Atsuko Kuroda, Hideki Sawaguchi, Yuzuru Hosoe, Takashi Kawabe, Hajime Aoi, Hiroaki Muraoka, Yoshihisa Nakamura, Kazuhiro Ouchi, “Realization of 52.5 Gb/in2 perpendicular recording,” J. Magn. Magn. Mater., vol. 235, pp. 241-244, 2001.

[10]. On-line announcement of shipment of perpendicular recording hard disk drives by Toshiba Corporation. http://www.toshiba.co.jp/about/press/2004_12/pr1401.htm

[11]. Newspaper article, Asahi Shimbun May 21, 2005. “’Perpendicular recording’ is commercialized”.

[12]. Shun-ichi Iwasaki, “Perpendicular Magnetic Recording –Its Development and Realization-,“ Proceedings of the Japan Academy Series B, vol 85, no. 2, pp. 37-54, Feb. 2009.

[13]. An IDC infographic, “Where in the world is storage”, 2013. Source: http://www.emc.com/leadership/digital-universe/index.htm

[14]. Yoichiro Tanaka, Hiroaki Muraoka, Shun-ichi Iwasaki, “Perpendicular Magnetic Recording; from invention to commercialization,” The 5th History of Electro-Technology Conference (HISTELCON 2017) A1-3, Aug. 7, 2017.

Supporting materials (supported formats: GIF, JPEG, PNG, PDF, DOC): All supporting materials must be in English, or if not in English, accompanied by an English translation. You must supply the texts or excerpts themselves, not just the references. For documents that are copyright-encumbered, or which you do not have rights to post, email the documents themselves to ieee-history@ieee.org. Please see the Milestone Program Guidelines for more information.


Please email a jpeg or PDF a letter in English, or with English translation, from the site owner(s) giving permission to place IEEE milestone plaque on the property, and a letter (or forwarded email) from the appropriate Section Chair supporting the Milestone application to ieee-history@ieee.org with the subject line "Attention: Milestone Administrator." Note that there are multiple texts of the letter depending on whether an IEEE organizational unit other than the section will be paying for the plaque(s).

Please recommend reviewers by emailing their names and email addresses to ieee-history@ieee.org. Please include the docket number and brief title of your proposal in the subject line of all emails.