title: Superexchange-mediated ferromagnetic coupling in two-dimensional Ni-TCNQ networks on metal surfaces.
abstract: We investigate the magnetic coupling of Ni centers embedded in two-dimensional metal-coordination networks self-assembled from 7,7,8,8-tetracyanoquinodimethane (TCNQ) molecules on Ag(100) and Au(111) surfaces. X-ray magnetic circular dichroism measurements show that single Ni adatom impurities assume a spin-quenched configuration on both surfaces, while Ni atoms coordinating to TCNQ ligands recover their magnetic moment and exhibit ferromagnetic coupling. The valence state and the ferromagnetic coupling strength of the Ni coordination centers depend crucially on the underlying substrate due to the different charge state of the TCNQ ligands on the two surfaces. The results suggest a superexchange coupling mechanism via the TCNQ ligands.
authors: Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, D-70569 Stuttgart, Germany.
authors: N
authors: N
authors: Abdurakhmanova
authors: T-C
authors: TC
authors: Tseng
authors: A
authors: A
authors: Langner
authors: C S
authors: CS
authors: Kley
authors: V
authors: V
authors: Sessi
authors: S
authors: S
authors: Stepanow
authors: K
authors: K
authors: Kern