IEEE Magnetics Society Newsletter

Perpendicular Magnetic Recording: Beyond 100 to 1000 Gigabits per Square Inch Jack H. Judy University of Minnesota

The challenges facing perpendicular magnetic recording beyond an incredibly high areal density of 100 to 1000 gigabits/in2 are to achieve high thermal stability with high signal amplitude and high media signal-to-noise ratio for low bit-error rate. Meeting these challenges will require double-layer, 50 to 25 nm thick media with extremely uniform magnetic clusters, 10 to 5 nm in diameter; a low-noise magnetic underlayer with high saturation flux density of 10 to 20 kG and permeability of 100 to 50; average surface roughness of 0.2 to 0.1 nm; remanent magnetization of 200 to 400 emu/cm3; unity squareness without any demagnetizing field correction; and remanent coercivity of 5 to 10 kOe. Such media will be written with sub-nanosecond rise times of 0.5 to 0.25 ns using a microstrip, single-turn, perpendicular-pole head, and read with a 10 to 20 percent giant magnetoresistance spin-valve head. The lecture will review the physics and development of perpendicular and longitudinal magnetic recording. The key problems encountered in the development of each will be discussed. In particular, the fundamental differences and limitations imposed by recorded bit demagnetizing fields; superparamagnetic, thermally-activated time decay of remanent magnetization; crystalline and superlattice multilayer surface magnetic anisotropies; grain size distribution; and media bit, transition, and track-edge noise will be illustrated with experimental data and micromagnetics simulations. A storage roadmap will be used to show how perpendicular magnetic recording may be able to achieve an areal density of 1 terabit/in2 by 2005.

Jack H. Judy received the S.B., S.M., and E.E. degrees in electrical engineering from the Massachusetts Institute of Technology in 1957, 1959, and 1961, respectively, and the Ph.D. degree from the University of Minnesota in 1965. He worked on a magnetic thin film memory in the IBM Systems Development Laboratory, Poughkeepsie, New York, and on a magneto-optical recording system in the IBM Advanced Technology Laboratory, Boulder, Colorado. Since 1969, he has been with the Department of Electrical Engineering at the University of Minnesota, becoming a full Professor in 1979. He has directed research on magneto-optics of soft magnetic films and experimental studies of the micromagnetics of bit transitions of digital magnetic recording in high-coercivity thin film media. In 1984, he established The Center for Micromagnetics and Information Technologies at the University of Minnesota. He has published over 200 papers on magnetic information storage technology.
Dr. Judy is a Senior Member of the IEEE.

Professor Alex Hubert died on February 16, 1999 on the South Erlangen campus of the Friedrich-Alexander-Universität Erlangen-Nürnberg, suffering a fatal heart attack during the lunch hour. We have lost an outstanding scientist who has made significant contributions to the understanding of magnetic structures and their technical implications.

Alex Hubert was born on May 14, 1938 in Darmstadt. His father, Alois Hubert, was an engineer. Alex received his high school diploma in Leverkusen and became a physics student at the University of Bonn in 1957. He moved to the University of Munich where he received his diploma in physics in 1962. He continued his studies in Munich under the direction of Professor Jakob Kranz, completing his doctoral studies in 1964 with the dissertation "Zur Analyse der magnetischen Bereichsstrukturen des Eisens" (On the analysis of magnetic domain structures in iron).

I first met Alex Hubert during a visit to Munich, then one of the centers of research in magnetism in Germany at both universities and at the Siemens Research Laboratory. This first encounter started a long friendship which later, after we married and had children, included both of our families. At the time of my visit, reprints of Alex's first publication had just became available: J. Kranz and A. Hubert "Die Moeglichkeiten der Kerrtechnik zur Beobachtung magnetischer Bereiche [The potential of the Kerr technique for observing magnetic domains], Z. angew. Phys. 15, 220- 232 (1963), which prominently graces my extensive library of important reprints. After two years as an assistant in Dr. Kranz's laboratory, two important events took place in Alex Hubert's life in 1966. He married Heidemarie Fiedler in Ottobeuren and he accepted a position as scientific collaborator at the Max-Planck-Institute fur Metallforschung in Stuttgart, in the Physics Department, directed by Professor Alfred Seeger. Among his many distinguished colleagues were Helmut Kronmüller, as well as Takao Suzuki who held a post-doctoral position at the same institute.

In 1973/74 Alex Hubert was a guest scientist at the Thomas J. Watson IBM Research Laboratory in Yorktown Heights. He wrote his "Habilitationsschrift" (a dissertation written to qualify for an academic career in Germany) on the "Theory of Domain Walls in Ordered Media" in 1974 – it was published by Springer. (A. Hubert " Theorie der Domaenenwande in geordneten Medien", 386 pages [Springer, Berlin-Heidelberg-New York, 1974].)

In 1975 Alex Hubert accepted a position in Materials Sciences as an assistant professor (Akademischer Rat and Privatdozent) at the University of Erlangen-Nürnberg, advancing to the position of Professor in 1983. In 1981, he again spent six months with IBM Research in Yorktown Heights.

Alex Hubert was not only an outstanding scientist but also took his obligations as an educator very seriously, including activities in the faculty management of the affairs of the university. At the time of his death, he was a member of the Senate of the university, Head of the examing committee of the technical faculty, headed a study group in material science education, to name just a few of his university activities. Alex Hubert set an outstanding example of a top scientist taking on an unusually large share of the more mundane but equally important duties of an educator.

In 1986, Alex Hubert was a guest professor for six months at Carnegie Mellon University. He also spent sabbatical semesters at the Institute for Physikalische Hochtechnologie in Jena in 1991 and at the IFW (Institut fur Festkoerper- und Werkstofforschung) in Dresden 1996/1997.

It will not be possible to do full justice to his numerous scientific contributions in the short space allotted here. His first paper, cited above, has remained an important reference on the enhancement of the Kerr effect in magneto-optic observation. The method described to obtain improved contrast in domain observations is also employed in Faraday effect observations and remains an important technique applied in magneto-optic memory applications. Alex Hubert continuously perfected domain observation techniques, which became a major tool in his investigations of magnetic domain and wall structures. His studies of magnetic domain and wall structures ranged from bulk materials to single and multilayer thin films. He was an early pioneer in the use of numerical micromagnetic calculations made possible by the availability of modern computers. His calculations provided magnetization models which he was able to verify experimentally with the tools of domain and wall observation that he perfected.

Alex Hubert has been an author or co-author of 145 publications, many of them invited. The many students who obtained their doctorate under his guidance bear witness to his genius as a magnetician and educator.

In 1998, Hubert published a book on which he devoted many years of his life. I recall discussions with him on the early chapters in the 1980s. One of his former students, Rudolf Schäfer, collaborated with him in the production of "Magnetic Domains: The Analyses of Magnetic Microstructures". The book is truly outstanding. It is a most thorough, carefully researched work on this subject in the entire literature of magnetism. Not long before his death, in an exchange of e-mail with me, Alex was already considering a "second edition" with additional material (or a sequel). Needless to say, Alex frequently presented papers and contributed discussions at national and international conferences, which always displayed his extraordinarily thorough knowledge of the subject and his insight into all the details of the physical phenomena. At the St. Paul Intermag Conference in 1985, I was able to organize a special evening session on behalf of the education committee of the IEEE Magnetic Society dealing with domain observations in which the principal speakers were Alex Hubert and Bernell Argyle. It was the first time that some of Alex's early works (published in German) were presented in North America.

With the untimely death of Alex Hubert, the international magnetics community has lost one of its most distinguished members and I have lost not only a colleague who was often able to guide me through difficult concepts in domain and wall structure but also a good friend. Our deepest sympathy goes to his widow, Heidemarie, his daughters, Barbara, Eva (Dumsky) and family, Birgit, and his son, Christian.

F. J. Friedlaender with acknowledgement to Helmut Kronmüller for his help.

The 10th annual TMRC conference was held August 9-11, 1999, on the campus of the University of California, San Diego (UCSD) and was chaired by Ken Johnson. The sole topic of this year's conference was media. Thirty-seven invited papers were presented in six sessions. The topics covered were 100 Gb/in2 and Beyond, Media and Microstructure, Recording Physics, Tribology, High Data Rate and High RPM issues, and finally Tape and Optical Assisted Recording. This TMRC marked the third time the conference has focused on media related issues. Areal density capability is always a topic of much interest and this TMRC was no exception. Seagate presented details on a 16 Gb/in2 areal density demonstration, and HMT/ReadRite showed data on a 26 Gb/in2 demonstration in the poster session.

The poster sessions contained all the invited talks as well as selected work from other contributors with an emphasis on student presentations. Dr. Tu Chen, Chairman of the Board of Komag Inc., gave a special luncheon keynote speech entitled "The Evolution of Magnetic Film Disks: Past, Present, and Future." The conference reception was held at the Aerospace Museum in Balboa Park, San Diego.

TMRC '99 marked the first "all electronic" Magnetics Society conference. Author instructions, digests, reviews, and final manuscripts were handled completely by e-mail, Internet web page access, and diskette. The refereed articles will be published in the January 2000 version of IEEE Transactions on Magnetics.

The 44th Annual Conference on Magnetism & Magnetic Materials was held at the Fairmont Hotel in San Jose, California on Sunday through Thursday, November 14-18, 1999. The MMM conference is held annually to allow the international scientific and engineering community to present and learn about recent developments in fundamental and applied magnetism. The conference included nearly 1000 invited and contributed papers given in 95 oral sessions, poster sessions and invited symposia. Three special evening sessions were held, "Magnetism and Living Systems" held Sunday evening before the main body of the conference, "Tutorial on Challenges in Magnetic Recording" on Monday evening, and "Symposium on Imaging and Magnetic Reversal" on Wednesday evening.

In addition to the scientific program, attendees contacted vendors in an exhibit of services, equipment, materials, software and books from a variety of companies that was held adjacent to the poster sessions. In the same area, attendees gathered for the morning coffee service and the late afternoon bierstube. The conference social event was a reception at the Tech Museum of Innovation, held Tuesday evening.

The conference was sponsored jointly by the American Institute of Physics and the Magnetics Society of the IEEE with cooperation from the Minerals, Metals and Materials Society and the American Ceramic Society with contributions from Motorola Labs, EMTEC Magnetics GMBH, Hewlett-Packard, Imation, TDK Corp., Toda Kogyo Corp., NEC Corp., Quantum, Komag, Lake Shore Cryotronics, Inc., Innovative Instrumentation and San Diego Magnetics.

The next MMM conference will be held jointly with the INTERMAG conference at the San Antonio Marriott Rivercenter in San Antonio, Texas, USA, January 7-11, 2001.

	An interesting and colorful poster presentation at MMM 99.
	The majestic San Jose Fairmont Hotel, where MMM 99 was held.
	Conference attendees experimented with the exhibits at the San Jose Tech Museum.

The Institute of Electrical and Electronic Engineers, pars pro toto, "The Institute" is also warmly known to its members as aye-tripple-ee: IEEE. The beginnings of this organization date back to 1884 as the AIEE, the American Institute of Electrical Engineers. In 1963 the AIEE and the Institute of Radio Engineers, IRE, which had existed since 1912 merged. Because these two groups had a large number of members in common, they had come to realize that their general interests in electrical and electronic engineering lay together. So those common members joined forces to form the IEEE, with the determination to make it the premier scientific and educational organization. Such is the vision of IEEE: to advance global prosperity by fostering technological innovation, enabling members' careers and promoting community worldwide. Since the merger, electrical engineering has proven to be the learned profession at the forefront in most, if not all, modern technological development. The breath of the technologies involve are represented by 37 societies of IEEE. These technologies have proliferated into every facet of human endeavor and are largely responsible for the quality of life enjoyed in the world today. As the breath of these technologies from nuclear and oceanic science to computer hardware and software is viewed, it seems quite distant to remember the work of Faraday, Maxwell, Gauss, Heaviside, Joule, Ohm, Ampere, Volta, Watt, Weber, Tesla, Marconi and the other 19th century founders of this profession. However, that all may know, we celebrate the work of these founders symbolically in the logo of IEEE.

When the founding organizations were joined in 1963 there was considerable effort expended to unify and simplify logos of these organizations while at the same time retaining their historical significance. The result of this work is the IEEE logo that we know today. It is the symbol we often refer to in familiar terms as the kite and right-hand rule. And symbolic it is:

A committee headed by Alexander Graham Bell in 1893 designed the AIEE's first logo. It was a kite shaped badge with a periphery marked by a coil of gold wire. The midpoints were spanned by a galvanometer complete with a blued steel needle on an amber disk. In 1897 another AIEE logo was developed using two linked circles to describe the relationship between the electric and magnetic fields. In 1912 the IRE logo was developed using a triangle and arrows to represent these same electrical and magnetic forces using the configuration of the right-hand rule.

The use of the right-hand rule in the IEEE logo captures, in simplistic terms, the great mathematical foundations of the profession as described in Maxwell's Equations. The right-hand rule is symbolic of the mathematical relationship between the electric and magnetic fields. It serves as a reminder that electrical engineering, and the technologies that flow from it, are based on the calculus and higher orders of mathematics as would be expected of a learned profession.

In a similar manner the kite, as found in the original logo of the AIEE, represents the kite used by Benjamin Franklin when he discovered electricity in lightning. So the kite immortalizes discovery as an essential element of the engineering profession. One is immediately drawn to the effort expended by Edison as he tried filament after filament leading to the discovery of the incandescent lamp. Today, discovery remains the essential tool of a technologist. The kite represents discovery just as Edison's work provides us a definitive example of the discovery process.

The IEEE kite logo is shown without the tail and in a symmetrical diamond form. The geometry of diamond shaped kite with its right-hand rule can also be viewed as a stylized form of the Wheatstone bridge. It has been said that this bridge with its galvanometer also depicts the earliest observation of electrical phenomena by Thales, and the source of the word electricity. The bridge is used as a precise measurement tool. Folklore surrounding the Wheatstone bridge reminds us that the linemen of yesteryear used it to predict the location of a break in a telegraph line to within the distance between two poles. And further, they would often bet coffee on which pole the break was closest to. Hence, the diamond symmetry of the IEEE logo represents the technologist's use of precision instrumentation and exact measurement as indispensable tools of the profession.

The logo of the IEEE serves as a reminder to our diverse membership, that today, we but stand on the shoulders of the giants who founded our profession. As part of the master brand of IEEE, the logo serves as a reminder of the underlying unity of the technologies that have flooded to fill the world as the result of the practice of electrical and electronic engineering. Transcending language, this symbol has become known worldwide. It is expressive of those engineering tools that will continue to be used to foster technological innovation: advanced mathematics, measurement, instrumentation, and discovery. And in the end, providence willing, this logo will represent the engineers, scientists and technologists who will be known for promoting community worldwide.

Written by
W. Cleon Anderson
Director, Region 6

A new book, "Introduction to Magnetism and Magnetic Recording" by Prof. R. Lawrence Comstock of San Jose State University is now available. Prof. Comstock is well-known in the magnetic recording community in part for being co-author with M.L. Williams on the seminal paper "An Analytical Model of the Write Process in Digital Magnetic Recording", AIP Conf. Proc., Part 1, no. 5, 1971, pp. 738-742. (Magnetic recording has come a long way since 1971!)

This book serves as an introduction to the physics and materials science of magnetism together with an up-to-date coverage of digital magnetic recording fundamentals, components and systems. Theory and applications are covered as well as fabrication of components. Key topics include: