Spin transfer in a ferromagnet–quantum dot and tunnel-barrier-coupled Aharonov–Bohm ring system with Rashba spin–orbit interactions

Xi Chen 1 , 2 , Qing-Rong Zheng 1 and Gang Su 1 , 3
1College of Physical Sciences, Graduate University of Chinese Academy of Sciences,PO Box 4588, Beijing 100049, People’s Republic of China
2Institut de Physique et de Chimie des Matériaux de Strasbourg (IPCMS),UMR 7504 CNRS-ULP, 23 rue de loess, F-67034 Strasbourg, France

Received 26 October 2009, in final form 15 March 2010 Published 20 April 2010



The spin transfer effect in a ferromagnet–quantum dot (insulator)–ferromagnet Aharonov–Bohm (AB) ring system with Rashba spin–orbit (SO) interactions is investigated by means of the Keldysh nonequilibrium Green function method. It is found that both the magnitude and direction of the spin transfer torque (STT) acting on the right ferromagnet electrode can be effectively controlled by changing the magnetic flux threading the AB ring or the gate voltage on the quantum dot. The STT can be greatly augmented by matching a proper magnetic flux and an SO interaction at a cost of low electrical current. The STT, electrical current and spin current are uncovered to oscillate with the magnetic flux. The present results are expected to be useful for information storage in nanospintronics.