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Relay-Like Exchange Mechanism through a Spin Radical between TbPc2 Molecules and Graphene/Ni(111) Substrates
journal contribution
posted on 2016-10-11, 00:00 authored by Simone Marocchi, Andrea Candini, David Klar, Willem Van den Heuvel, Haibei Huang, Filippo Troiani, Valdis Corradini, Roberto Biagi, Valentina De Renzi, Svetlana Klyatskaya, Kurt Kummer, Nicholas
B. Brookes, Mario Ruben, Heiko Wende, Umberto del Pennino, Alessandro Soncini, Marco Affronte, Valerio BelliniWe
investigate the electronic and magnetic properties of TbPc2 single ion magnets adsorbed on a graphene/Ni(111) substrate,
by density functional theory (DFT), ab initio complete
active space self-consistent field calculations, and X-ray magnetic
circular dichroism (XMCD) experiments. Despite the presence of the
graphene decoupling layer, a sizable antiferromagnetic coupling between
Tb and Ni is observed in the XMCD experiments. The molecule–surface
interaction is rationalized by the DFT analysis and is found to follow
a relay-like communication pathway, where the radical spin on the
organic Pc ligands mediates the interaction between Tb ion and Ni
substrate spins. A model Hamiltonian which explicitly takes into account
the presence of the spin radical is then developed, and the different
magnetic interactions at play are assessed by first-principle calculations
and by comparing the calculated magnetization curves with XMCD data.
The relay-like mechanism is at the heart of the process through which
the spin information contained in the Tb ion is sensed and exploited
in carbon-based molecular spintronics devices.