Structural and magnetic properties of Cr in Cr/Ru(0001) multilayers

We present a study of the structural and magnetic properties of Cr in Cr/Ru(0001) multilayers grown by molecular-beam epitaxy. The atomic structure of Cr was investigated by various methods including reflection high-energy electron diffraction, x-ray diffraction, polarized x-ray-absorption fine and near-edge structure analysis. These investigations have revealed that Cr layers of up to three monolayer thickness show a slightly distorted hexagonal-close-packed structure induced by pseudomorphic growth on Ru(0001). A significant increase in atomic volume of up to 14% compared to the body-centered-cubic bulk structure was found for the Cr in the hcp structure. Moreover, weak ferromagnetism (<0.1μ_B) was found for the hcp Cr layers most likely due to a hybridization effect of the d bands of Cr and Ru at the interfaces as suggested by theory.