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

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 tau(Rx)/I-e (tau(Rx) is the spin-transfer torque acting on the right ferromagnet and I-e is the tunneling electrical current) does vary with the molecular fields. At two certain angles, tau(Rx)/I-e is independent of the molecular field of the right ferromagnet, resulting in two crossing points in the curve of tau(Rx)/I-e versus the relevant orientation for different molecular fields. (C) 2002 Elsevier Science B.V. All rights reserved.