Domain Wall Dynamics in Stepped Magnetic Nanowire with Perpendicular Magnetic Anisotropy

Micromagnetic simulation is carried out to investigate the current-driven domain wall (DW) in a nanowire with perpendicular magnetic anisotropy. A stepped nanowire is proposed to pin DW and achieve high information storage capacity based on multibit per cell scheme. The DW speed is found to increase for thicker and narrower nanowires. For depinning DW from the stepped region, the current density J_dep is investigated with emphasis on device geometry and material intrinsic properties. The J_dep can be analytically determined as a function of the nanoconstriction dimension and the thickness of the nanowire. Furthermore, J_dep is found to exponential dependent on the anisotropy energy and saturation magnetization, offering thus more flexibility in adjusting the writing current for memory applications.