Multiple Reflection Effect on Spin-Transfer Torque Dynamics in Spin Valves with a Single or Dual Polarizer

摘要

In this paper, spin-dependent multiple reflection effect on spin-transfer torque (STT) has beenrntheoretically and numerically studied in a spin valve nanopillar with a single or dual spin-polarizer.rnBy using a scattering matrix method, we formulate an analytical expression of STT that containsrnthe multiple interfacial reflection effect. It is found that the multiple reflections could enhance thernSTT e±ciency and reduce the critical switching current. The STT e±ciency depends on the spinrnpolarization of both the free layer and polarizer. In the nanopillars with a dual spin polarizer, thernmultiple reflections would cause an asymmetric frequency dependence on the applied current, albeitrnexactly the same parameters are used in all three ferromagnetic layers, indicating that the frequencyrnin the negative current varies much faster than that in the positive case.