报告人：Dr Joerg WUNDERLICH (Hitachi Cambridge Laboratory, Hitachi Europe Ltd, Cambridge, United Kingdom; Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic）

摘要：

The rich internal degrees of freedom of magnetic domain walls (DW) make them an attractive complement to electron charge for exploring new concepts of storage, transport, and processing of information.We utilize the tunable internal structure of a DW in perpendicularly magnetized GaMnAsP/Ga As ferromagnetic semiconductor and demonstrate devices in which piezo-electrically controlled magneticanisotropy yields large mobility variations for current driven DW motion. We directly observe and piezo-electric control the Walker breakdown separating two regimes with different mobilities. The piezo-electric control allows to experimentally assess the upper and lower boundaries of the characteristic ratio of adiabatic and non-adiabatic spin transfer torques in the current driven DW motion.

Apart from current induced DW motion, also optically generated electron spins can move DWs. The direction of DW motion depends on the photon helicity in our GaMnAsP/Ga As devices and we identify optical spin transfer torque (oSTT) as the underlying mechanism. We further discuss possibilities to apply and electrically control oSTT induced DW motion to thin magnetic metal films.Optically driven DW motion can be very efficient and high velocities maybe achieved since intrinsic DW pinning does not occur when the entire DW is simultaneously exposed to perpendicular polarized electron spins.

We also identify a polarization independent contribution for light-induced DW motion where the DW is attracted to the hot-spot generated by the focused laser light. Unlike magnetic field and current driven DW motion, light-induced DW motion provides an optical tweezers like ability to position and locally probe DWs.

Dr Joerg WUNDERLICH is a Senior Research Scientist in Hitachi Cambridge Laboratory, Hitachi Europe Ltd, Cambridge and he is holding a joint position in Institute of Physics, Academy of Sciences of Czech Republic in Prague. He obtained his PhD in a joint program with Institute of Fundamental Electronics, CNRS (Orsay, France) and the Max Planck Institute of Microstructure Physics (Halle an der Saale, Germany) in 2001. Then he joined Hitachi Cambridge Laboratory as a Research Scientist, and was promoted to current position in 2004. He has published 60 research papers including 1 Science, 1 Review of Modern Physics, 3 Nature Materials, 3 Nature Nanotechnology, 1 Nature Physics, 1 Nature Communications and 10 PRLs.

地点：中科院物理研究所D楼 D211会议室

联系人：金奎娟 研究员 （Tel：82648099）

邀请人：许秀来研究员（Tel：82649820）

主办单位：中国科学院光物理重点实验室