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Dr. Sebastian Loth

Max Planck Institute for Solid State Research, Stuttgart, Germany

Tuesday, June 12th, 2012 at 11:30:00 AM  

Chemistry Department - Polo Scientifico di Sesto Fiorentino

Published on-line at 11:35:20 AM on Wednesday, May 23rd, 2012

Nanomagnets on surfaces constructed atom by atom

STM-based atomic assembly as a new approach to explore magnetism at the cross-over from quantum mechanical to classical magnetic behavior.

Small nanomagnets consisting of just a few atoms provide well-defined model systems to explore the foundations of magnetism and quantum mechanical behavior of spins. In recent years scanning tunneling microscopy has developed the tools to measure magnetic properties of individual atoms with high precision. We study transition metal atoms adsorbed to a monolayer thin decoupling layer of Cu2N on copper. The N atoms form a network of polar covalent bonds that incorporates the adsorbed atoms. This creates a quasi-molecular environment for the atomic spins. We use the STM tip's interaction with the surface to construct precisely defined assemblies of interacting atoms.

Inelastic electron tunneling spectroscopy verifies the formation of correlated spin states. We find high magnetic anisotropy and strong exchange coupling energies in the 1-10 meV range [C.F. Hirjibehedin et al. Science 317, 1199 (2007)]. Time-resolved measurements give access to the corresponding electron-spin relaxation behavior [S. Loth et al. Science 329, 1628 (2010)]. We map the variations of the spin relaxation time for spins in different local environments and find that minute interactions with spins at a distance of up to 3 nm have a measurable influence. I will show that antiferromagnetic interaction can lead to the emergence of extremely stable magnetic states with Néel-type order for structures with as few as six atoms [S. Loth at al. Science 335, 196 (2012)].

These experiments establish STM-based atomic assembly as a new approach to explore magnetism at the cross-over from quantum mechanical to classical magnetic behavior.

For further informations, please contact Prof. Roberta Sessoli.