Micromagnetic computation for wall coercivity caused by magnetic nonuniformity

TLDR: In this paper, a two-dimensional grid system representing the magnetization direction in a magnetic film plane was used to study the wall coercivity caused by magnetic nonuniformity.

Abstract: The wall coercivity caused by the magnetic nonuniformity has been studied numerically. The Landau‐Lifshits‐Gilbert (LLG) equation is integrated by an explicit scheme of the modified Dufort‐Frankel method. The computation was carried out for a two‐dimensional grid system representing the magnetization direction in a magnetic film plane. Typical magnetic parameters for magneto‐optic recording media were assumed. Spatial variations of uniaxial anisotropy were treated as the magnetic nonuniformity. The validity of our numerical approach was demonstrated with preliminary one‐dimensional computations, compared to analytical solutions. A wall coercive field of 2.5 kOe was observed for the wall coupling with a pinning site (30‐A width and 360‐A spacing along the wall) of 10 times larger anisotropy compared to the ordinary region. A two‐dimensional anisotropy variation (K=106–107 erg/cm3) with a wavelength larger than 60 A also caused a wall coercivity on the order of 1 kOe, compared to those in magneto‐optic recording media. It was also found that a fine pinning site on the order of 100 A caused a notable coercivity for the bubble domain wall surrounding it.