Title: Electrical Gating of Magnetism in (Ga,Mn)As and Beyond
Speaker: Professor Hideo Ohno（Research Institute of Electrical Communication, Tohoku University）
Time: 9:30(AM), May 21, 2010
Venue: Academic Salon, Institute of Semiconductors, CAS
Abstract: It was shown that one can switch on and off the ferromagnetic phase of magnetic III-V semiconductor through changing its carrier concentration by applying external electric-fields, owing to the hole-induced nature of ferromagnetism. This has opened up a new route toward manipulation of magnetism and magnetization, not resorting to magnetic fields nor to spin currents. Recent results on probing the change of magnetic moments by direct magnetometry revealed the dependence of spontaneous magnetic moment ms on applied electric field. The observed electric-field dependence of TC and ms and the TC ？ p0.2 relationship revealed by transport measurements were shown to be well accounted for by the p-d Zener model taking into account the non-uniform carrier distribution in thin films (<5 nm). If time allows, I show an anomalous reduction of the magnitude of the anomalous Hall effect as temperature is reduced in (Ga,Mn)As thin layers with high conductivity (> 200 S/cm). Although still not fully conclusive, electric-field gating was used to investigate the origin of this reduction . This work was supported in part by the R & D for Next-Generation IT Program (MEXT) and by the FIRST program of JSPS.
About speaker：
Prof. Hideo Ohno received the B.S., M.S. and Ph.D. degrees from the University of Tokyo in 1977, 1979 and 1982, respectively. 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 is heading an IT program on ”Development of Universal Low-Power Spin Memory” funded by MEXT and is also Research Director of Semiconductor Spintronics Project, Exploratory Research for Advanced Technology, Japan Science and Technology Agency. His current research interests include physics and applications of spin-related phenomena in semiconductor as well as in metal-based nanostructures. He has authored and coauthored about 300 journal papers that cover the areas from compound semiconductor materials and devices to nonmagnetic semiconductor, ferromagnetic-semiconductor and metal spintronics. Dr. Ohno received the IBM Japan Science Award (1998), the IUPAPMagnetism Prize (2003), Japan Academy Prize (2005) and the 2005 Agilent Technologies Europhysics Prize. He is currently on the editorial board of several international journals including Virtual Journal of Nanoscale Science and Technology, Solid State Communications, and Semiconductor Science and Technology.