Spin-flip scattering effect on the current-induced spin torque in ferromagnet–insulator–ferromagnet tunnel junctions

Zhen-Gang Zhu, Gang Su ∗ , Biao Jin, Qing-Rong Zheng

Department of Physics, The Graduate School of the Chinese Academy of Sciences, PO Box 3908, Beijing 100039, China

Received 30 October 2002; accepted 6 November 2002 Communicated by V.M. Agranovich

Abstract We have investigated the current-induced spin transfer torque of a ferromagnet–insulator–ferromagnet tunnel junction by taking the spin-flip scatterings into account. It is found that the spin-flip scattering can induce an additional spin torque, enhancing the maximum of the spin torque and giving rise to an angular shift compared to the case when the spin-flip scatterings are neglected. The effects of the molecular fields of the left and right ferromagnets on the spin torque are also studied. It is found that τRx /Ie (τRx is the spin-transfer torque acting on the right ferromagnet and Ie is the tunneling electrical current) does vary with the molecular fields. At two certain angles, τRx/Ie is independent of the molecular field of the right ferromagnet, resulting in two crossing points in the curve of τRx/Ie versus the relevant orientation for different molecular fields. 

2002 Elsevier Science B.V. All rights reserved. PACS: 73.40.Gk; 73.40.Rw; 75.70.Cn