Spin-transfer based MRAM with reduced critical current density

摘要

A magnetic random access memory device include a spin torque MRAM cell (100) having a reduced switching current (I_c) wherein standard materials may be used for a free layer (108). A fixed magnetic element (112) polarizes electrons passing therethrough, and the free magnetic element (108) having a first plane anisotropy comprises a first magnetization (130) whose direction is varied by the spin torque of the polarized electrons. An insulator (110) is positioned between the fixed magnetic element (112) and the free magnetic element (108), and a keeper layer (104) positioned contiguous to the free magnetic element (108) and having a second plane anisotropy orthogonal to the first plane anisotropy, reduces the first plane anisotropy and hence reduces the spin torque switching current (I_c). The keeper layer (104) may include alternating synthetic antiferromagnetic layers (132, 134) of magnetization approximately equal in magnitude and opposite in direction.