Spin Transfer in Spin-Orbit Coupled Nanostructures

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

TECHNICAL SUMMARY: This award supports theoretical research and education in the properties of nanostructures which have the potential to function in future electronic devices which are based on electron spin dynamics instead of traditional charge dynamics. Researchers will investigate the mechanisms of spin transfer and spin transport in molecular magnetic nanostructures, in static and dynamic cases, where the spin-orbit interaction is significant. Research builds on the known property that spin degrees of freedom in materials couples to orbital motions of electrons and the observation that this plays an important role in molecular nanostructures where one observes current-induced magnetization reversal and anomalies in the Kondo effect. Research will identify how the spin-orbit interaction in nanostructures can be controlled by changing geometry, adsorbed molecules, chemical composition, or applied electric field. The nanostructures under study are nanoscale magnetic molecules (diameter of a few nm), particularly single molecule magnets with substantial spin-orbit coupling, (i) adsorbed onto nonmagnetic or magnetic metal surfaces, and (ii) bridged between nonmagnetic or magnetic electrodes. The specific objectives of the research are (a) to quantify the spin-orbit interaction for the molecular nanostructures using a first-principles method, and (b) to investigate the effect of the spin-orbit interaction on the spin transfer and spin transport through the molecular nanostructures, using both model Hamiltonians and realistic atomic-scale simulations based on a first-principles method and nonequilibrium Green?s function method. Especially when the magnetic molecules are adsorbed on a ferromagnetic surface or electrodes, large spin transfer is expected due to a strong coupling between the molecules and the surface or electrodes. The proposed realistic simulations will lead to results of almost immediate relevance to experiment (such as an amount of spin transfer for given nanostructure) and to theory (for example, the coupling between the molecules and the electrodes), as well as will provide guidance to theory and experiment. This research will be conducted with the participation of graduate students, who will be trained in modern methods of theory and computer simulation as applicable to nanoscale systems, preparing them for careers in science and nanotechnology. The PI will connect the research activities with the educational activities at her institution, thereby making connections between the course material and real-world applications and up-to-date research to allow the students to acquire perspectives and skills in tackling scientific problems. Finally the research will be performed in collaboration with scientists from the US and abroad, strengthening and enriching the US ties to the international community. NON-TECHNICAL SUMMARY: This award supports theoretical research and education in the properties of nanostructures which have the potential to function in future electronic devices which are based on electron magnetic characteristics associated with the spin of the electron instead of traditional charge dynamics which is the basis of normal electrical current. Researchers will investigate the mechanisms of spin transfer and spin transport in ultra small scale molecular magnetic nanostructures. Research builds on the known property that electron spin couples to motion of electrons and the observation that this plays an important role in molecular nanostructures where one observes current-induced magnetic phenomena. Research will identify how the spin-motion interaction in nanostructures can be controlled by changing geometry, adsorbed molecules, chemical composition, or applied electric field. This research will be conducted with the participation of graduate students, who will be trained in modern methods of theory and computer simulation as applicable to nanoscale systems, preparing them for careers in science and nanotechnology. The PI will connect the research activities with the educational activities at her institution, thereby making connections between the course material and real-world applications and up-to-date research to allow the students to acquire perspectives and skills in tackling scientific problems. Finally the research will be performed in collaboration with scientists from the US and abroad, strengthening and enriching the US ties to the international community.