Multilayer relaxation and search for ferromagnetic order at the (100) surface of bulk paramagnetic vanadium

Abstract

Low-energy-electron-diffraction (LEED) intensity measurements and multiple-scattering analysis for V(100), supported by accurate characterization of surface impurity concentrations based on Auger-electron spectroscopy, are used to obtain a meaningful extrapolation of the first-layer relaxation to the clean surface value: ${d}_{12}=1.36\ifmmode\pm\else\textpm\fi{}0.05\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$, corresponding to ${\ensuremath{\Delta}}_{12}=\ensuremath{-}10%\ifmmode\pm\else\textpm\fi{}3%$ relative to the bulk value ${d}_{0}=1.514\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. A high-sensitivity probe for surface magnetism based on magneto-optic Kerr effect polarimetry using the cleanest surfaces achieved in the LEED experiment $(\ensuremath{\sim}5%\phantom{\rule{0.3em}{0ex}}\mathrm{C})$ yields a (sensitivity limited) null result with an estimated upper limit of $0.05\phantom{\rule{0.3em}{0ex}}{\ensuremath{\mu}}_{B}$/surface atom. These results are discussed within the framework of related experiments and in relation to the predictive accuracy of ab initio calculations that explore the surface structure and magnetism of V(100) both of which are sensitive to different approximations for the exchange-correlation potential in density-functional theory.