Interlayer exchange, magnetotransport, and magnetic domains in Fe-Cr layered structures (invited) (abstract)

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The Fe-Cr layered structure is a model system where both the antiferromagnetic-type interlayer coupling and the magnetoresistivity (MR) effect due to antiparallel alignment occur with good strength. For a better theoretical understanding there is a need for more detailed and reliable data. Here the most recent results for the Fe-Cr system will be presented and will be compared with data obtained by other groups and on other systems. By means of light scattering from spin waves and M(H) curves obtained via the magneto-optic Kerr effect, we have examined the interlayer coupling A₁₂ as function of the Cr thickness d_Cr and confirmed the oscillatory behavior first reported by another group. Our method clearly shows that the coupling becomes ferromagnetic between the ranges of antiferromagnetic coupling, which was not yet clear from available data. For large d_Cr the oscillations fade out and the coupling remains weakly antiferromagnetic. In the case of (100)-type growth we also find a fine structure for A₁₂ (d_Cr) as expected from theory. We have also analyzed the new MR effect by using a formalism based on a modified Fuchs–Sondheimer approach. From this we conclude that the MR effect is due to a spin-dependent electron scattering at the Fe-Cr interfaces. For the diffusive scattering rate at these interfaces we obtain ~50% for spin up and only 4% for spin down. Finally, the results of domain investigations will be presented. For samples with wedge-type interlayers, the gross features of these domains reflect the oscillatory behavior of the coupling. Further investigations suggest the existence of a quadratic term in the coupling energy favoring a perpendicular magnetization alignment of the two films with respect to each other. Journal of Applied Physics is copyrighted by The American Institute of Physics.