Monatomic Au wire with a magnetic Ni impurity: Electronic structure and ballistic conductance

The influence of a magnetic impurity (Ni atom) on the electronic, magnetic, and Landauer conductance properties of a monatomic Au wire is studied by first-principles density-functional calculations. We compare two adsorption geometries: bridge and substitutional. We find that the Ni atom remains magnetic in both cases; however, in the bridge geometry, the total spin is close to 1/2 and the symmetry of the hole is d(3z)(2)-r(2) while in substitutional it is larger than 1/2 with two degenerate holes with symmetry d(yz) and d(zx). By using the Buttiker-Landauer theory, we find that in the first case the ideal, frozen spin conductance is somewhat diminished by the Ni impurity, although quite sensitive to calculation details such as the position of the empty Ni d and s states, while in the substitutional case conductance remains close to the ideal value G(0) (=2e(2)/h) of the pristine gold wire.