Low critical current density of magnetic spin valve with perpendicular anisotropy

In 1996, Slonczewki [1] and Berger [2] independently predicted an important effect: spin-transfer torque (STT), which can manipulate magnetization orientation in magnetic multilayer nanostructure. This effect can provide a local magnetization manipulation rather than using a long-rang Oersted field induced by a remote current. Due to STT potential applications in magnetic random access memory (MRAM), STT switching magnetization in nanostructure has attracted intense attention in recent years. Achieving low critical current density is one of most challenging aspect for reducing power consumption. Many methods had been attempted by using lower saturation magnetization free layer [3], double antiparallel fixed layers structure [4], microwave assisted spin-transfer torque [5], soft core in free layer [6], or nanocurrent channels (NCCs) [7] in free layer to reduce critical current density.