Low Current Driven Vertical Domain Wall Motion Memory with an Artificial Ferromagnet

We propose a new structure of vertical domain wall (DW) motion memory with artificial ferromagnet to achieve high DW controllability. The artificial ferromagnet is composed of periodically stacked ferromagnetic bilayers with relatively large and small exchange stiffness constants (Aex), which refer to as strong coupling layers and weak coupling layers. By optimizing Aex and the magnetic anisotropy of the weak coupling layers, DW width and position can be easily controlled. Furthermore, micromagnetic analysis shows that low critical current density for DW motion down to 2 ×1010 A/m2 can be achieved as we increase the Aex of weak coupling layers to larger than 2 pJ/m.