Spin-polarized Shockley state at Ni(111) free surface and at Ni-Cu-based structures on Cu(111) surface

The electronic structure of Cu(111) and Ni(111) free surfaces and of Ni-Cu structures on the Cu (111) surface is studied from ab initio calculations. Systems ending on a Ni layer are found to be magnetic. The spin splitting of the Ni d band raises the position of some minority Ni d(xz,yz) states which then lie in the energy range where the Shockley state should appear. This results in a strong sp-d hybridization of the spin-down components which furthermore depends on the k momentum. As a result, the Shockley state of Ni-terminated surfaces is spin polarized. The ab initio results are compared to recent STM experiments.