Magnetics Society Distinguished Lecturers for 2009
Contact individual Distinguished Lecturer at the email addresses indicated. Each Distinguished Lecturer makes his/her own schedule, so contact them early before their schedules are filled. For additional assistance and/or further information contact the Distinguished Lecturer Coordinator (Roy Chantrell, rc502@york.ac.uk).
The Evolution and Revolutions in Disk Drive Recording
Dr Michael Mallary
IEEE Fellow
Since 1956 the areal density of hard disk drives, HDDs, has increased by eight orders of magnitude through a process of evolution punctuated by a number of important revolutions. The disk evolved for three decades through many generations of painted gamma ferric oxide particulate media with in plain orientation. During this time areal density was increased from 2 kilo-bits/inch2 (2kbpsi) for IBM’s RAMAC to ~20Mbpsi .
The technology has seen a number of revolutions. In the mid 1980s the first (non-magnetic!) revolution was a diamond like carbon over coat for media that is key to its durability. The next revolution was the introduction of read sensors based on Giant Magneto-Resistive films with improved sensitivity. HDD proceeded to evolve up to ~100 Gbpsi on this technology base.
By the mid 1990’s Prof. Stanley Charap of Carnegie Mellon University calculated that longitudinal recording would start to experience thermal decay of the data at densities of ~40 Gbpsi. In response to this impeding crisis, the Ultra-High Density Recording project was initiated by Prof. Mark Kryder (CMU) under the National Storage Industry Consortium umbrella. The UHDR team established the reality of the problem and proposed strategies to delay the crisis to ~100 Gbpsi. Key amongst these was to increase tracks per inch faster than bits per inch.
The UHDR theory team also determined that magnetizing the media perpendicular to the disk could extend magnetic recording by almost an order of magnitude beyond the thermal decay limit of longitudinal recording. Perpendicular HDDs are now being shipped at ~300Gbpsi. Key head innovations in achieving this density are the use of the the Shielded Pole writer invented by the author, and the Tunneling Magneto-Resistive reader with an MR effect approaching 100%.
The 30-40% per year growth in areal density will soon drive perpendicular recording to its thermal decay limit near 1 Tbpsi in demonstrations and less in products. Two revolutionary technologies are being developed to deal with this. Heat Assisted Magnetic Recording will allow high anisotropy media to be written at elevated temperatures thus allowing for finer thermally stable grains to be written. Bit Patterned Media will allow the recording of a bit on a single grain as compared to scores of grains with unpatterned media. The promise and problems of these technologies will be discussed in detail.
Michael Mallary is an IEEE Fellow and Distinguished Lecturer for 2009. He received his S.B. degree in physics from the Massachusetts Institute of Technology in 1966, and Ph.D. degree in Experimental High Energy Physic from the California Institute of Technology, in 1972.
He was a post doctoral fellow at the Rutherford Laboratory for from 1972-1974 and an Assistant Professor of physics at Northeastern University from 1974-1978. There he participated in an experiment at Fermi Laboratory that produced early evidence for the fifth quark using a 300 ton solid iron magnet. From 1978 to 1980 he worked at the Magnetic Corporation of America designing large superconducting magnets for MHD, MRI, energy storage and magnetic separation.
In 1980 he joined the Digital Equipment Corporations effort to produce thin film heads for disk drive recording as a head modeler and designer. Here he invented the Shielded Pole perpendicular recording head which has demonstrated superior performance over the conventional monopole head and is now in very disk drive shipped today. He also invented the Diamond inductive head which doubles the effective number of turns. In addition he has contributed to the theory of: flux conduction in thin film heads at high frequency; low bit aspect ratios for high density in the thermal decay limit; and tilted write fields for improved switching. His publications and patents have significantly advanced the field of magnetic recording.
Mike Mallary is presently working on Heat Assisted Magnetic Recording, Shingle Recording and 2 Photon Recording at the Seagate Technology Research Center in Pittsburgh. He has authored and co-authored 67 issued patents and 52 publications including “Our Improbable Universe” (ISBN 1-56858-301-X).
Contact: Michael Mallaey, Seagate Research, 1251 Waterfront place, Pittsburgh, PA 15222, USA, e-mail: Mike.Mallary@seagate.com.
Biomedical nanomagnetics : A spin through new possibilities
Kannan M. Krishnan
University of Washington, Seattle
Two of the principal challenges in biomedical nanoscience and personalized medicine are: a) the detection of disease at the earliest possible time prior to its ability to cause damage (diagnostics and imaging) and b) delivering treatment at the right place, at the right time whilst minimizing unnecessary exposure (targeted therapy with a triggered release). The former is dominated by optical methods, emerging “life on a chip” systems and the versatile magnetic resonance imaging technology. The latter remains an ongoing challenge.
In this context, we have been developing multifunction platforms for therapy, diagnostics and imaging based on functionalized, biocompatible, nanomagnetic molecular probes. Our work encompasses innovations in synthesis and functionalization, controlled self-assembly, advanced characterization, a wide-range of magnetic measurements and modeling to tailor their behavior for high moment or high frequency applications and carrying out cytotoxicity and biocompatibility studies. Currently, in vitro (magnetic separation and diagnostic relaxometry), in vivo (hyperthermia treatment of cancer, triggered drug delivery) and imaging (contrast enhancement in MRI and the development of a novel magnetic particle imaging microscope) applications are all being pursued.
This first part of the lecture will include an overview of nanotechnology, size-dependent magnetic behavior and the emerging field of biomedical nanomagnetics. This will be followed by a comprehensive discussion of our current work in these areas highlighting the fundamental principles behind our research in the context of emerging technological and clinical opportunities.
Kannan M. Krishnan received his B. Tech in Mechanical Engineering from IIT, Kanpur (India) in 1978, his MS in Materials Science from SUNY, Stony Brook in 1980 and his Ph.D in Materials Science from the University of California, Berkeley in 1984. He subsequently held various scientific and teaching positions at Lawrence Berkeley National Laboratory, UC Berkeley before joining the University of Washington, in 2001, as the Campbell Chair Professor of Materials Science and Adjunct Professor of Physics. He has also held visiting appointments at the Hitachi Central Research Laboratory (Japan), Tohoku University, Danish Technical University, University of Sao Paolo, University of Western Australia and Indian Institute of Science.
Prof. Krishnan is well recognized for both research and teaching. His many awards include the Guggenheim Fellowship (2004), the Rockefeller Bellagio Residency Fellowship (2008), the Burton Medal (Microscopy Society of America, 1992), Japanese Society for the Promotion of Science Senior Scientist Fellowship (2002), the University of Washington, College of Engineering Outstanding Educator Award (2004) and an appointment as the Professor-at-large at the University of Western Australia (2006-8). He is a Fellow of the American Association for the Advancement of Science and the Institute of Physics (London), and has served on the editorial boards of the Journal of Materials Science and Journal of Physics D: Applied Physics.
Prof. Krishnan’s inter-disciplinary research interests are in magnetic nanostructures and thin film heterostructures, biomedical nanomagnetics, oxide spin electronics, advanced materials characterization and structure-property correlations at relevant length scales. All the projects are vertically integrated from the underlying science to their engineering (information storage, MEMS, magnetoelectronic devices) and biomedical (diagnostics, imaging and therapeutics) applications.
Contact: Prof. Kannan M. Krishnan, Department of Materials Science, University of Washington, Seattle, WA 98195-2120, USA; telephone: 1-206-543-2814; fax: 1-206-543-3100; e-mail: kannanmk@u.washington.edu.
Spintronics: Nanoscience and Nanoelectronics
Hideo Ohno
Tohoku University
Spintronics explores the physics of interplay between spin and charge in condensed matter. It is one of the most active areas of magnetism. In particular, electrical manipulation of spin and magnetization in nanostructures allows us not only to study the interplay but can also be utilized to reverse magnetization direction, which is of great importance to nanoelectronics. In my lecture, I describe the nanoelectronics side and the science side of spintronics by discussing two topics that delineate the significance and technological importance of such spin manipulation in condensed matter.
I am sure not many of the audience are old enough to remember that magnetic memory was once preferred main memory for modern digital computers. There were reasons it was replaced by semiconductor memories. However, with the advances in spintronics, i.e. the recent development of giant tunnel magnetoresistance and current-induced magnetization switching in magnetic tunnel junctions, it appears that a comeback of magnetic memory may be possible, which now combines the nonvolatile capability of magnetic nanostructure with all the functionalities of current and future complementary metal-oxide-semiconductor (CMOS) integrated circuits. I also show that this hybrid magnetic tunnel junction/CMOS integrated circuit approach can solve many of the major challenges current integrated circuit technology are facing.
On the science side and on out further in the future, I turn to hole-induced ferromagnetism in Mn-doped III-V semiconductors (in particular, GaAs and InAs). This offers a variety of opportunities to explore new and/or unique spintronics physics. Ferromagnetism and magnetization in these materials can be manipulated by various means; by changing its carrier concentration by electric fields and/or by spin-current flowing along with the electric current. In the latter, our latest study on an empirical scaling law found in the creep regime of the current-driven domain walls showed that spin-torque driven creep is quite different from magnetic-field driven (and thus energy driven) creep, belonging to a new and different universality class. In the former, an electrical control of magnetization direction through manipulating magnetic anisotropy by electric-fields was shown to be possible. This opens up a unique opportunity for manipulating magnetization direction solely by electronic means, not resorting to magnetic-field, spin-current, mechanical stress, nor multiferroics.
Hideo Ohno received the B.S., M.S. and Ph.D. degrees from the University of Tokyo in 1977, 1979 and 1982, respectively. He spent one year as a visiting-graduate student at Cornell University, Ithaca, USA from 1979. He joined the Faculty of Engineering of Hokkaido University, Sapporo, Japan in 1982. He was a visiting scientist at IBM T. J. Watson Research Center from 1988 to 1990. He moved to Tohoku University, Sendai, Japan as Professor in 1994, where he is currently Director of Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication. He has authored and coauthored more than 300 papers that cover the areas of semiconductor materials and devices to physics and applications of spin-related phenomena in semiconductors as well as in metal-based nanostructures. Professor Ohno received the IBM Japan Science Award (1998), the IUPAP Magnetism Prize (2003), Japan Academy Prize (2005), Presidential Prize for Research Excellence, Tohoku University (2005) and the 2005 Agilent Technologies Europhysics Prize. He has been a Fellow of the Institute of Physics (IOP) since 2004, an honorary professor of Institute of Semiconductors, Chinese Academy of Sciences since 2006 and a Fellow of the Japan Society of Applied Physics (JSAP) since 2007. Tohoku University appointed him as a distinguished professor in 2008.
Contact: Professor Hideo Ohno, Laboratory for Nanoelectronics and Spintronics, Research Institute of Electrical Communication, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan; telephone and fax: +81-22-217-5553; e-mail: ohno@riec.tohoku.ac.jp
Controlling Magnetism with Light
Theo Rasing
Institute for Molecules and Materials Radboud University Nijmegen, The Netherlands
The interaction of light with magnetic matter is well known: magneto optical Faraday or Kerr effects are frequently used to probe the magnetic state of materials. or manipulate the polarisation of light . The inverse effects are less known but certainly as fascinating: with light one can manipulate magnetic matter, for example orient their spins. Using femtosecond laser pulses we have recently demonstrated that one can generate ultrashort and very strong (~Tesla's) magnetic field pulses via the so called Inverse Faraday Effect. Such optically induced magnetic field pulses provide unprecedented means for the generation, manipulation and coherent control of magnetic order on very short time scales, including the complete reversal of a magnet with a single 40 femtosecond laser pulse. In principle this opens the way for all-optical recording of magnetic bits at extremely high data rates. The basic ideas, including their limitations, behind these discoveries will be discussed and illustrated with recent results.
Theo Rasing (26 May 1953, Didam) obtained his degree in physics (cum laude) from the Radboud University Nijmegen in 1976, where he also gained his doctorate in 1982. After postdoctoral stays at UC Berkeley (IBM fellowship) he became staff scientist and deputy program leader at the Lawrence Berkeley Laboratory, where he developed nonlinear optical techniques for surface and interface studies. In 1988 he was appointed associate and in 1997 full professor of physics in Nijmegen. He is the founder and director of the Nijmegen Centre for Advanced Spectroscopy (NCAS), member of the board of the Dutch NanoNed and founder of NanoLab Nijmegen that makes its expertise and infrastructure available to the commercial sector. In 2007 he received the Physica Prize from the Netherlands Physical Society and in 2008 he received the Spinoza price, the highest scientific award from the Netherlands Organisation for Scientific Research NWO. To date, his research has yielded more than 300 publications in international journals, including Nature, Science and Physical Review Letters. He is also the initiator and coordinator of various large national and international partnership programmes.
Theo Rasing is a pioneer in the development of new linear and nonlinear optical techniques for studying and manipulating molecules and materials with an emphasis on nanometer length and femtosecond time scales. His research is mostly focused on the static and dynamic properties of magnetic nanostructures and multilayers. For this he developed the technique of Magnetization induced Second Harmonic Generation and various ultra sensitive pump-probe methods. His most recent and most successful research in the field of spin dynamics is that into the manipulation of magnetism using light.
Contact: Prof. Th.H.M. (Theo) Rasing (Radboud University Nijmegen) t: +31 24 365 3102, th.rasing@science.ru.nl; http://www.ru.nl/ssi/
