title: Role of hydrogen in giant spin polarization observed on magnetic nanostructures.
abstract: We demonstrate that the giant spin contrast observed by scanning tunneling microscopy for double-layer Coislands on Pt(111) is caused by adsorbates at the apex of the Cr-coated W tip. The most likely candidate, in ab initio simulations, is hydrogen. Here, the electron charge is highly polarized by the adjacent Cr layers. The hydrogen adsorption site is shown to change from hollow to on top due to the electric field at the tip apex, created by the tunnel voltage.
authors.affiliation: Surface Science Research Centre and Department of Physics, University of Liverpool, Liverpool L69 3BX, United Kingdom.
authors.forename: Werner A
authors.initials: WA
authors.lastname: Hofer
authors.forename: Krisztián
authors.initials: K
authors.lastname: Palotás
authors.forename: Stefano
authors.initials: S
authors.lastname: Rusponi
authors.forename: Tristan
authors.initials: T
authors.lastname: Cren
authors.forename: Harald
authors.initials: H
authors.lastname: Brune