Fieldlike and Dampinglike Spin-Transfer Torque in Magnetic Multilayers

Abstract

We investigate the spin-transfer torque in a magnetic multilayer structure by\nmeans of a spin-diffusion model. The torque in the considered system,\nconsisting of two magnetic layers separated by a conducting layer, is caused by\na perpendicular-to-plane current. We compute the strength of the field-like and\nthe damping-like torque for different material parameters and geometries. Our\nstudies suggest that the field-like torque highly depends on the exchange\ncoupling strength of the itinerant electrons with the magnetization both in the\npinned and the free layer. While a low coupling leads to very high field-like\ntorques, a high coupling leads to low or even negative field-like torques. The\ndependence of the different torque terms on system parameters is considered\nvery important for the development of applications such as STT MRAM and\nspin-torque oscillators.\n