[TABLE OF CONTENTS]
Conventional electronics has ignored the spin on the electron. Besides its fundamental unit charge, the electron has a magnetic moment due to its quantum of angular momentum. Things began to change in 1988, with the discovery of giant magnetoresistance in metallic thin film stacks. This led to the development of spin valves and magnetic tunnel junctions, which allowed magnetic recording to ride the tiger of 100% year-on year growth of recording density for the past ten years. Tunnel junctions are the active elements for most schemes for nonvolatile magnetic random-access memory, which will be briefly surveyed.
These devices, which underpin the multi-billion dollar magnetic recording industry, are nothing more than sophisticated magnetoresistors, the simplest two-terminal electronic device. If we are to see a second generation of spin electronics, it will be necessary to develop more complex devices such as a three-terminal spin transistor with gain. Here magnetic semiconductors are required, or at least the ability to manipulate spin-polarized currents in normal semiconductors. The puzzling new family of dilute magnetic oxides, such as ZnO:Co or SnO2:Mn, and the emerging class of d0 ferromagnets such as HfO2 or CaB6 may produce a new paradigm for magnetism in solids, and support entirely new device concepts. A major challenge is to separate spin and charge currents in solids, and transmit information magnetically, without dissipation.
Michael Coey received a BA degree in physics from Cambridge University in 1966, and a PhD from the University of Manitoba in 1971. He worked as a researcher in the Centre National de la Recherche Scientifique in the 1970s, before moving to Trinity College Dublin, where he has been Professor of Experimental Physics since 1986.
Michael Coey has broad interests in magnetism, spanning materials hard and soft, crystalline and amorphous, metallic, semiconducting and insulating as well as magnetic phenomena and devices. He coordinated the ‘Concerted European Action on Magnets’ (1984-94), a pioneering group of academic and industrial researchers devoted to all aspect of the understanding, development an application of rare-earth iron permanent magnets. More recently, he led the Oxide Spin Electronics Network, OXSEN 1996-2000. Currently he is Deputy Director of Ireland’s nanoscience centre CRANN. He serves as Divisional Associate Editor of Physical Review Letters and on the editorial board of the Journal of Magnetism and Magnetic Materials.
His main research interests at present are in spin electronics, including magnetic semiconductors, as well as magnetotransport and magnetoelectrochemistry. He has published more than 500 papers, and is co-author of books on Magnetic Glasses and Permanent Magnetism. Michael Coey is the recipient of the Charles Chree medal of the Institute of Physics, and the gold medal of the Royal Irish Academy. He is a fellow of the Royal Society, and a Foreign Associate of the National Academy of Science.
[ Go To Top ]
Massive Information: Exploitation and Security
Magnetic information technologies have enabled the amount of data stored last year to increase, by some estimates, by nearly one order of magnitude over that of the previous year. Personal data stores have reached into the terabyte regime and enterprise stores are now measured in petabytes. Digital music and video recorders have brought large data stores into the consumer market. About 80 percent of these data are unstructured (i.e., not indexed), inherently unstructureable (e.g., audio, images, or DNA data), rapidly changing (e.g., intelligence data and medical records), or held as an object within an otherwise structured database (such as memo fields, voice records, etc.). To find something of interest and ultimately extract actionable knowledge from these unstructured data, like finding specific needles in a haystack of many needles, one must process all of the data stored — not just an index as is often done with structureable data. Furthermore, since data stored are increasing at a rate faster than electronic processing capacity (as guided by Moore’s Law) our ability to manage this information in reasonable times is further aggravated.
New and tractable processing approaches, yielding performance improvements in excess of 100,000 over conventional systems, may be possible over storage networks and large disk arrays with capabilities that include line-speed compression, encryption, signal processing and other broad functionality. In this presentation I will explore emerging systems and hybrid concepts that circumvent conventional, sequential processor and bus-bandwidth limits, making data movement more effective and efficient, as well as enabling content-enhanced storage on ingest. Early critical applications include intelligence (both government and commercial), medicine, scientific research, financial services, and enterprise storage networks.
Ronald S. Indeck received the B.S.E.E., M.S.E.E., and Ph.D. degrees from the University of Minnesota. He is a Founder and Technical Advisor to Exegy, Inc. He was a National Science Foundation Research Fellow at Tohoku University in Sendai, Japan. Since 1988 he has been in the Department of Electrical Engineering at Washington University, where he is the Das Family Distinguished Professor and Director of the Center for Security Technologies. He has published more than 50 peer reviewed technical papers and has been awarded more than 20 patents. He has received the National Science Foundation Presidential Young Investigator Award, the Missouri Bar Association’s Inventor of the Year Award, the IBM Faculty Development Award, the Washington University Distinguished Faculty Award, the IEEE Centennial Key to the Future Award, and the IEEE Young Professional Award.
Indeck is a Fellow of the IEEE and a member of the American Physical Society. He is on the board of the Federal Bureau of Investigation’s InfraGard program. He has served several international conferences and was co-chairman of the 2002 International Magnetics Conference. He has served as an editor of IEEE Transactions on Magnetics and as president of the IEEE Magnetics Society. Indeck currently consults for industry and government, and leads research in projects of recording physics, magnetic devices, security, and data mining in massive databases.
[ Go To Top ]
Beyond the Limits of Magnetic Recording: an Itinerant Magnetician Looks at Hysterical Loops
For several decades there have been declarations that digital magnetic recording as we know it is about to reach the ultimate limit of areal density. Technological advances have enabled steady progress primarily through simultaneous scaling of dimensions and tolerances over several orders of magnitude and use of materials with larger energy densities. In the 1990’s it became clear that then current approaches would be limited to about 40 Gb/ sq. in. by the combined requirements that individual grains have reversal barriers of above 40 kT for long term data retention and that a bit cell contain 100 or more grains for adequate media signal-to-noise. Recent areal density demonstrations at about 6 times that limit have been possible with perpendicular recording and improved materials, but perhaps we are again nearing the ultimate physical limits, unless a novel idea comes along. In addition to perpendicular recording, technologies suggested to extend the limits include patterned media, thermally-assisted writing and tilted media. We’ll discuss the potential advantages and challenges of these approaches. Areal density is primarily limited by write head materials and fabrication tolerances, while data-rate is limited by sensor technology which must provide several times kT of signal energy (and low noise levels) to detect a bit. Sensors have evolved from inductive heads to anisotropic magneto-resistive heads to in-plane giant magneto-resistive (GMR) devices with CPP (current across the gap) GMR devices with spin-tunneling sensors also under consideration. We’ll discuss the attributes of these technologies and the anticipated requirements. Powerful error correction codes will also be required if we are to reach 1 Tb/ sq. in, so attention must be paid to writing, reading and arithmetic.
Mason L. Williams received a B.S. in Engineering in 1964 from the California Institute of Technology, and the M.S.E.E. degree in 1966 and a PhD in Electrical Engineering with Physics minor in 1970 from the University of Southern California where he studied under Professor Jan Smit.
In 1970, Dr. Williams joined IBM in San Jose, California, initially in a Manufacturing Research department. In his first year he was assigned to work with R. Larry Comstock on characterization and testing of experimental magnetite film media. That collaboration led to the so-called “Williams-Comstock” analytical model of digital magnetic recording. In 1982, he joined the Magnetic Recording Institute and managed an investigation of perpendicular magnetic recording briefly. In 1985 he became manager of Advanced Recording Heads at the IBM Almaden Research Center in San Jose. In that role he managed the development of micro-magnetic modeling for magneto-resistive head elements and the first building of spin-valve head test structures to verify biasing techniques. In 1992, Dr. Williams became the IBM representative to the Ultra-High Density Magnetic Recording Head project of the National Storage Industry Consortium, aimed at 10 Gb/sq in technology. In 1996, he became part of the Extremely High Density Recording Strategy Team at INSIC. In 1999, he was elected to the IEEE grade of Fellow. In 2001, he was selected as an IBM Master Inventor, and holds several recording head patents. At the end of 2002, Dr. Williams retired from IBM and joined Hitachi Global Storage Technologies. He worked on novel perpendicular head approaches and then focused again on recording physics and integration modeling until retiring from Hitachi in 2005.
[ Go To Top ]
[TABLE OF CONTENTS]