Abstract
Domain wall dynamics in a perpendicularly magnetized system is studied by means of micromagnetic simulations in which disorder is introduced as a dispersion of both the easy-axis orientation and the anisotropy constant over regions reproducing a granular structure of the material. High field dynamics show a linear velocity-field relationship and an additional grain size dependent velocity shift, weakly dependent on both applied field and intrinsic Gilbert's damping parameter. We find the origin of this velocity shift in the nonhomogeneous in-plane effective field generated by the tilting of anisotropy easy axis introduced by disorder. We show that a one-dimensional analytical approach cannot predict the observed velocities and we augment it with the additional dissipation of energy arising from internal domain wall dynamics triggered by disorder. This way we prove that the main cause of higher velocity is the ability of the domain wall to irradiate energy into the domains, acquired with a precise feature of disorder.
Highlights
Domain wall (DW) dynamics in ultrathin films with high perpendicular magnetocrystalline anisotropy (PMA) has received a lot of attention over the last years [1,2,3] since these structures present several advantages over in-plane magnetized materials towards their potential use in spintronic devices, such as narrower domain walls and better scalability
DW velocity measurements from micromagnetic simulations are shown in Fig. 2(a) for samples of width W = 2 μm with various grain sizes and α = 0.015, together with the one-dimensional (1D) model calculations
We have used micromagnetic simulations to investigate domain wall motion in magnetic systems where a granular structure and interfacial effects are expected to play a role in introducing material inhomogeneities affecting DW dynamics
Summary
Domain wall (DW) dynamics in ultrathin films with high perpendicular magnetocrystalline anisotropy (PMA) has received a lot of attention over the last years [1,2,3] since these structures present several advantages over in-plane magnetized materials towards their potential use in spintronic devices, such as narrower domain walls and better scalability. Recent works have focused their attention on the role played by motion and annihilation of vertical Bloch lines (VBL) inside the DW and how these processes have a strong impact on the DW velocity [11]. Such features cannot be taken care of in the one-dimensional model and, micromagnetic simulations have become an essential tool for an interpretation of these complexities, allowing for a better understanding of experimental data
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