A new mechanism of controlling magnetic states by electric currents has been discovered through an internationally collaborative work, published in journal of Nature Nanotechnology.
Current technologies for writing, storing, and reading information are either charge-based or spin-based. Semiconductor flash or random access memories are prime examples as charge-based devices but they are relatively fragile against electric noises caused by such as radiation and temperature change, leading to data loss. Spin-based devices, storing information as the position of the north and south pole of the magnet, hold promise. For developing these technologies, scientists have been exploring for a new electric control of the magnetic states, which ultimately combines the merits of both charge and spin-based devices.
In this work, the researchers took a permanent magnet GaMnAs and accelerated some of the electrons inside the permanent magnet by electric field. These accelerated electrons created a new internal magnetic cloud via the spin-orbit interaction. This current-induced magnetic moment was able to interact and control the surrounding permanent magnet, and the researchers detected that the poles of the permanent magnet moved. It is found that the observed effect exploits the quantum geometrical phase, so-called the Berry phase, existing in the momentum space of electronic band structures in specific materials. The scientists will pursue the power of the spin-orbit interaction further for new spintronic materials, in a view of using it for future nano-electronic devices.
Research Area : "New Materials Science and Element Strategy"
Research Theme : "Functional Materials with novel interface enginnering/electonic states, and the development of future ultralow power magnetisation switching"
H. Kurebayashi, Jairo Sinova, D. Fang, A. C. Irvine, T. D. Skinner, J. Wunderlich, V. Novak, R. P. Campion, B. L. Gallagher, E. K. Vehstedt, L. P. Zarbo, K. Vyborny, A. J. Ferguson and T. Jungwirth. “An antidamping spin-orbit torque originating from the Berry curvature”
Nature Nanotechnology, Published online 2nd March 2014
Hidekazu Kurebayashi, Ph.D.
Lecturer, Department of Electronic & Electrical Engineering
London Centre for Nanotechnology/UCL
Koji Matsuo, Masashi Furukawa, Oaku Hiromi
Green Innovation Group, Department of Innovation Research, JST