Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 40: Spin Effects in Molecules at Surfaces (jointly with DS, MA)
O 40.3: Talk
Wednesday, March 13, 2013, 10:00–10:15, H23
Superexchange-mediated ferromagnetic coupling in two-dimensional Ni-TCNQ networks on metal surfaces — •Sebastian Stepanow1, Nasiba Abdurakhmanova1, Tzu-Chun Tseng1, Alexander Langner1, Christopher Kley1, Violetta Sessi2, and Klaus Kern1,3 — 1MPI-FKF Stuttgart — 2ESRF Grenoble — 3EPFL Lausanne
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 (XMCD) 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.