Surface structure determination of Pd ultrathin films on Ru(0001): Possible magnetic behavior

Abstract

Nowadays, ultrathin films play a fundamental role in modern materials science and technology. Recently, several theoretical works indicate that the magnetic properties of Pd ultrathin films could be controlled by structural parameters of the film, and much work has been done to study induced magnetic properties of ultrathin Pd films grown on different substrates. For the epitaxy of Pd monolayers on Ru(0001), it was not clear if Pd grows in an hcp or fcc structure and a detailed surface structure determination was not available for this system. In this study, Pd films with thicknesses ranging from submonolayer up to approximately 15 ML were grown on a Ru(0001) single crystal substrate under UHV conditions, and the electronic structure, surface crystallography, and magnetism were investigated by multiple (experimental and theoretical) techniques: x-ray photoelectron spectroscopy and diffraction using conventional $\mathrm{Mg}\phantom{\rule{0.2em}{0ex}}K\ensuremath{\alpha}$ and synchrotron radiation sources, low- and high-energy electron diffraction, magneto-optical Kerr effect measurements, and density-functional theory calculations. The electronic structure, surface crystallography, and magnetism of the Pd films are discussed in detail.