Domain wall pinning at an interface step defect

Abstract

We study the magnetization of a thin uniaxial ferromagnetic film on a two-sublattice uniaxial antiferromagnetic substrate near an interface step defect. The step defect produces two distinct regions where opposite sublattices of the antiferromagnet adjoin the interface. We show that the proximity interaction with the substrate leads to the formation and pinning of a Neel domain ́ wall centred at the step edge. The equilibrium pattern is obtained using a numerical procedure which allows for rearrangement of the magnetization of the ferromagnet, which adjusts itself under

the effect of the interface field. Our results indicate that the wall profile is rather close to a free- wall pattern; however, the proximity interaction may lead to considerable reduction of the domain

wall width. We find that the interface coupling controls the magnetization for weak fields applied along the easy axis. In this case the magnetization results from rigid displacement of the wall, favouring the growth of the domain magnetized in the field direction. The wall detaches from the defect, and the magnetization saturates, when the applied-field strength reaches the value of the interface exchange field associated with the proximity interaction. For a weak external field applied perpendicular to the step edge direction, the magnetization is due to the orientation of the domains in the field direction. In this case saturation occurs for much larger applied-field strength.