Structure and magnetism of Mn/Ru and Mn/Fe/Mn/Ru superlattices prepared by molecular-beam epitaxy

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Abstract
Our recent study on Fe/Ru superlattices revealed a hexagonal structure, a reduced magnetic moment (1.7 μB) in the plane of the layers, and an antiferromagnetic coupling between the Fe mediated through Ru. We inserted just one plane of manganese between the Fe and the Ru to determine the interface influence on the structural and magnetic properties in Mn/Fe/Mn/Ru superlattices by means of local and selective techniques such as x-ray-absorption and Mössbauer spectroscopy. We describe the growth of Mn on Ru by reflection high-energy electron diffraction and by Auger electron microscopy experiments to realize the superlattices Mn/Ru. Complementary results obtained from x-ray-diffraction and macroscopic magnetization measurements allowed us to quantitatively describe our systems. The Mn structure was found to be identical to the Fe structure in Fe/Ru superlattices. We show that there is no solid solution between Fe and Ru at the interface in Fe/Ru which could be responsible for the four Fe magnetically inactive layers. We obtain the same reduced magnetic moment for the next Fe layer and a moment of few tenths of μB for a Mn layer. Finally we confirm once more the excellent quality of the interface in these superlattices which did not give giant magnetoresistance.