Dependence of hard-axis anisotropy field on domain wall width for current-induced domain wall motion in nanowires

The dependence of the hard-axis anisotropy field on the domain wall width for current-induced domain wall motion in perpendicularly magnetized anisotropic nanowires was investigated using micromagnetic simulations. The hard-axis anisotropy field in nanowires was estimated by varying the magnetic anisotropy constant and the exchange stiffness constant, and the hard-axis anisotropy constant was calculated from the energy differences of the Bloch and Néel walls. As a result, when the stable domain wall is a Bloch wall, the hard-axis anisotropy field and the intrinsic critical current velocity decrease with increasing domain wall width, whereas when the stable domain wall is a Néel wall, they increase with increasing domain wall width. It was clarified that the intrinsic critical current velocity can be expressed as a function of the domain wall width, even though the analytical solution indicated that the critical current velocity would be monotonically reduced by decreasing the domain wall width.