Super-exchange mediated antiferromagnetic coupling in a two-dimensional metal-organic coordination network synthesized directly on a metal surface.

PALOMA MACHAÍN; JAVIER FUHR; J. ESTEBAN GAYONE; HUGO ASCOLANI

San Carlos de Bariloche

Congreso; XXIII Latin American Symposium on Solid State Physics; 2018

Gerencia Física-CAB, CNEA

Low-dimensional magnetic nanostructures show interesting phenomena with a high potential for their integration in magnetic recording, spintronic, and sensing devices. In this regard, a considerable effort is dedicated to produce and investigate two dimensional (2D) metal-organic coordination networks (MOCNs) deposited on non-magnetic metal surfaces, where the periodically arranged metal centers are magnetically coupled by the organic ligands.[1-3] However, realization of these systems has been challenging since the interaction with the metal surface can significantly modify the chemical and electronic states of both organic and inorganic components. In this work we show that functionalization of surfaces is an efficient strategy to tune surface-network interactions aiming to true 2D systems. We recently synthesized a quasirectangular MOCN comprised of Mn atoms and TCNQ (7,7,8,8-tetracyanoquinodimethane) molecules deposited on the 0.5ML Sn-Cu(100) surface alloy. This MOCN would present, according to our DFT+U calculations, super-exchange mediated anti-ferromagnetic (AF) coupling between the Mn atoms. The calculations predict a magnetic moment for the Mn atoms close to 5 uB, corresponding to a high-spin (S=5/2) state. From calculations with different magnetic orderings we estimated an AF coupling with nearest neighbors of J=0.96 meV, much larger than the coupling reported for TCNQ-Mn on Au(111) [3]. Remarkably, while on the Sn-Cu(100) surface alloy the charge transfer to the molecules is active, the chemical interaction between the Mn adatoms and the surface is significantly weaker than on Au(111). Therefore, the synthesized system constitutes a promising model to investigate the puzzle of the factors that influence the magnetic properties of MOCNs confined to metal surfaces.