Depinning Field of Vortex Domain Wall in Wide Magnetic Wires with Asymmetric Notches Using Magneto-Optical Kerr Effect Microscopy

We examined the pinning and depinning fields of the vortex domain wall (VDW) in wide permalloy wires to better understand VDW dynamic behavior. Our sample device has differently designed notches at the center of a 2-μm-wide wire. The notch depth ratio ranged from 0.2 to 0.8, and the asymmetric angles of the notches are 45°, 60°, and 75°. The depinning field was found to have two distribution ranges, similar to how the depinning field depends on VDW chirality in submicron size width wire. Our results also showed that the VDW depinning behavior of a wide wire is the same as that of a narrow wire. The asymmetric notch angle affected the depinning field, which was similar to the results of simulation with 400-nm wire. This suggests that the wide wire depinning field is similar to that of narrow wire.