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Physics Colloquium, October 15, 2002Advanced Magnetic Materials and Transducers: Enabling Information Explosion and Magnetic NanotechnologyShan X. WangStanford UniversityAdvanced magnetic materials and transducers are critical building blocks in numerous engineering devices such as bio-magnetic sensors, magnetic hard disk drives, magnetic inductors, electronic article survrence, and magnetic levitation trains. Their physical length spans from nanoscale to thousands of miles. They are essential for the explosive growth in the storage capacity of hard drives at least by two orders of magnitude in the 1990s. The use of magnetic media with ever higher coercivities requires write heads to deliver more intense magnetic field, which in turn requires higher saturation magnetization of the soft magnetic material used in write heads. As an example, the talk will describe films of a new soft magnetic material based on Fe-Co-N with a saturation magnetization of 24 kG, exceeding that of any currently available soft magnetic material, with a superior permeability of over 1000 up to 1.2 GHz. They are very promising for extending the superparamagnetic limit in magnetic recording while achieving a data rate of over 2.4 Gbit/s, as well as for applications in gigahertz integrated inductors and other electromagnetic devices. Rapid development in giant magnetoresistive materials and novel spin-dependent devices has enabled read heads to detect ever-smaller bits written in hard disk drives. In search of new magnetoresistive materials, we encounter many interesting scientific questions. The talk will describe work on electron specular reflection and specular spin valves using an in-situ resistance and magnetoresistance probe. The challenges in utilizing spin valves and spin-dependent tunnel junctions for future generations of hard disk drives will also be discussed. Finally, new applications of advanced magnetic materials and transducers in emerging magnetic nanotechnologies and magnetoelectronics, particularly bio-magnetic sensing and DNA detection, will be highlighted.
Shan Wang received the B.S. degree in physics from the University of Science and Technology of China in 1986, the M.S. in physics from Iowa State University in 1988, and the Ph.D. in electrical and computer engineering from Carnegie Mellon University in 1993. He is an associate professor in the Department of Materials Science and Engineering and jointly in the Department of Electrical Engineering at Stanford University. He is currently the director of the Stanford Center for Research on Information Storage Materials (CRISM). He was a Frederick Terman Faculty Fellow at Stanford University (1994-1997). His current research interests include magnetoresistive materials and spin electronics, magnetic inductive heads and soft magnetic materials, magnetic recording physics, magnetic nanotechnology, and bio-magnetic sensors. He has published over 80 papers on these subjects. He is co-author, with Alex Taratorin, of Magnetic Information Storage Technology (Academic Press). Dr. Wang served as a member of IEEE Magnetics Society Administrative Committee (1998-2000, 2002-present) and chair of the Santa Clara Valley Chapter of IEEE Magnetics Society (1999-2000). He is an IEEE Distinguished Lecturer from the Magnetics Society (2001-2002). 3.30 p.m., Smith Laboratory, Room 1005Refreshments served in Smith 1094 at 3:00 p.m. |
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