Micromagnetic study of domain-wall pinning characteristics with grooves in thin films

Abstract

The pinning characteristics of a 180° domain wall with grooves are investigated using the micromagnetic simulation. The depinning fields required to pull the wall out of the grooved region were strongly related to the pinning characteristics at each step edge. The depinning field difference between the wall movement directions was improved by the increase of the lower depinning field compared to that with the steplike thickness change. It was also found that the depinning fields for various groove widths were almost constant and the wall displacement was further suppressed by the narrower groove having the vertical edge.

Domain-wall pinning by steplike thickness change in magnetic thin film

“…5 In the previous work, micromagnetic simulation has reported that steplike thickness change along a domain wall can produce wall pinning in an in-plane magnetization thin film. 6,7 The simulation results have indicated that a bidirectional pinning effect for magnetic fields applied along the magnetic domain was obtained at the step.…”

“…[6][7][8][9] As illustrated in Fig. 1, a steplike thickness change ͑⌬h͒ along the domain wall ͑x direction͒ is assumed to clarify the wall-pinning characteristics with thickness change.…”

“…Material parameters used in the simulation are as follows: saturation induction 4M s = 8000 G, uniaxial anisotropy constant K u = 3200 ergs/ cm 3 , exchange constant A =10 −6 erg/ cm, gyromagnetic ratio ␥ = 1.76ϫ 10 7 ͑s Oe͒ −1 , and damping constant ␣ = 0.5. 6,7 The grid element spacing is 5 nm for the film thickness h ഛ 300 nm and 10 nm for h Ͼ 300 nm, respectively. The easy axis is along the x direction and magnetic fields ͑H p ͒ are applied along the magnetic domain.…”