Magneto-optical analysis of stripe elements embedded in a synthetic antiferromagnet

Domain structures and magnetic reversals of ferromagnetic micron stripe patterns embedded in an interlayer exchange coupled Co90Fe10 trilayer acting as a synthetic antiferromagnet were investigated. The patterning was achieved by means of ion irradiation through a lithographically processed mask, which changes the irradiated parts into ferromagnetic elements. The embedded stripes fabricated by this technique have been investigated and compared to stripes patterned by reactive ion etching. Using Kerr microscopy the domain structure and the shape of the magnetic reversal have been studied. Observed differences in the switching behavior will be explained by modifications of the magnetic material properties, e.g. anisotropy and saturation magnetization due to the ion irradiation. Irradiated 2 µm wide stripes show a collective switching with quasi-domains during the magnetic reversal. In this process interactions of the transversal magnetization component with the adjacent non-irradiated antiferromagnetically coupled trilayers are observed. Two possible mechanisms suspected to mediate these interactions are discussed. On the one hand a slight opening of the coupling angle between magnetization in top and bottom layer in the antiferromagnetic stripes leading to an effective magnetic moment. On the other hand a domain wall with its extended tail at the boundary between the two different kinds of stripes. The investigations are supported by micromagnetic simulations.