Controlling the domain wall dynamics in Co-rich magnetic microwires with graded magnetic anisotropy

We have shown after annealing Co-rich microwire in a temperature gradient, graded magnetic anisotropy is observed. In studied microwires annealed at variable temperatures, a gradual change in hysteresis loops along the length of the microwire from inclined to perfectly rectangular is observed. Accordingly, the remagnetization process along the length of such wires changes its character. In Co-rich microwire segments with squared hysteresis loops, single domain wall propagation is observed. At the same time the magnetization rotation is observed in the region with an inclined hysteresis loop. The domain wall propagation in Co-rich microwire with graded magnetic anisotropy is essentially non-uniform. A single domain wall propagates at a non-uniform speed in the region of the wire with graded magnetic anisotropy. At a certain position of the microwire with graded anisotropy inside the magnetization coil, the direction of the domain wall propagation changed to the opposite. The domain wall velocities differ significantly for cases where the magnetization switching starts from a region with graded magnetic anisotropy or from a region with rectangular hysteresis loops. The observed features of the domain wall dynamics in Co-rich microwires with graded magnetic anisotropy are discussed, taking into account the domain wall inertia and changes in the demagnetizing field during magnetization reversal.