Spintronics: Nanoscience and Nanoelectronics
 
Tohoku University
Jeudi 01/10/2009, 11h00
Bât. C5 P.421A, CEA-Grenoble

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

Contact : Vincent BALTZ

 

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