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 τ/Ie (τ Rx is the spin-transfer torque acting on the right ferromagnet and Ie is the tunneling elcetrical current) does vary with the molecular fields. At two certain angles, τ/Ie is independent of the molecular field of the right ferromagnet, resulting in two crossing points in the curve of τ/Ie versus the relevant orientation for different molecular fields. PACS numbers: 73.40.Gk, 73.40.Rw, 75.70.Cn Typeset using REVTEX