Distance- and spin-resolved spectroscopy of iridium atoms on an iron bilayer

The induced spin polarization of Ir atoms on a ferromagnetic Fe double layer on W(110) has been investigated with spin-polarized scanning tunneling microscopy. An unoccupied state is observed with a spin polarization exceeding $60\phantom{\rule{0.16em}{0ex}}%$ that is inverted with respect to the Fe layer. This inversion is due to the tunneling gap acting as an orbital and spin filter. Distance dependent measurements show that the spin polarization remains approximately constant over the entire experimentally accessible range, from far in the tunneling regime to 1 \AA{} from the point of contact formation. This is corroborated by density functional theory calculations which show that the inversion of spin polarization occurs within 0.5 \AA{} of the adatom.