Imaging of domain wall motion in small magnetic particles through near-field microscopy

Abstract

We report magneto-optical scanning near-field optical microscopy images for 4×4×0.08 μ m3 and 16×16×0.08 μ m3 low magnetic anisotropy Co70.4 Fe4.6 Si15 B10 particles. Measuring magneto-optical differential susceptibility we acquired images of the domain wall movement driven by an applied magnetic field with a spatial resolution better than λ4. For the 4×4×0.08 μ m3 sized particle, a sequence of 27 magneto-optical differential susceptibility images reveals the evolution of the magnetic domain structure between positive and negative saturation fields passing through the four-domain flux-closure magnetization structure. On the 16×16×0.08 μ m3 particle, we studied the role of the oscillating driving field on the susceptibility distribution. Comparing the different magneto-optical differential susceptibility sequences, the role of the shape anisotropy on the field induced domain wall movement is evidenced. Micromagnetic simulations were used to provide a better understanding of the domain wall movement. © 2006 American Institute of Physics.