Magneto-optic imaging of domain walls in ferrimagnetic garnet films

Magneto-optic (MO) imaging is based on Faraday rotation of a linearly polarized incident light beam illuminating a sensitive MO layer (MOL) placed in close contact to the sample. For in-plane magnetized layers of Lu3-x,Bi,Fe5-y,GayO12 ferrimagnetic garnet films, zig-zag domain formation occurs whenever the sample stray parallel field component, H-parallel to, changes sign. Considering the anisotropy, exchange and magnetostatic energies in the Neel tails, and the contribution of an applied magnetic field, it is possible to describe the zig-zag walls that separate domains with opposite in-plane magnetization. The size of the walls decreases with the spatial derivative of H-parallel to. We studied the evolution of these domains as we steadily forced the change in sign of H-parallel to to shorter length scales, from hundreds to a few microns. We describe the samples used to control the change in sign of H-parallel to at the MOL plane, and we analyze the images that evolve from zig-zag walls to much more complex closed domain structures. (c) 2007 Elsevier B.V. All rights reserved.