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

Domain structures and the magnetic reversals of micron stripe patterns embedded in a weakly antiferromagnetically exchange coupled Co90Fe10/Ru/Co90Fe10 trilayer were investigated. Patterning was achieved by means of ion irradiation through a lithographically defined mask. Irradiated parts become ferromagnetic due to interfacial intermixing. The embedded stripes fabricated by this technique are compared to stripes patterned by reactive ion etching. Using magneto-optical Kerr microscopy the domain structure and the shape of the magnetic reversal for both kinds of stripes have been studied. Observed differences in the switching behavior are 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 of the embedded stripes with the adjacent non-irradiated antiferromagnetically coupled trilayers are observed.Two possible mechanisms suspected to mediate these interactions are discussed: A deviation of the antiparallel magnetic orientation in the synthetic antiferromagnetic material leading to an effective magnetic moment, as well as a domain wall at the boundary of two different kinds of stripes. The latter investigation is supported by micromagnetic simulations.