PGI-1 Talk: Prof. Dr. Fernando Delgado

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30 Oct 2019 11:30

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PGI Lecture Hall

Abstract:

Single magnetic atoms on surfaces are the ultimate limit of the magnetic domains used for data storage. Interestingly, they can display spin-excitations, as probed by inelastic electron tunneling spectroscopy (IETS), and long relaxation times, exceeding the microsecond time scale. Their magnetic moments can be manipulated by spin-polarized currents or give place to magnetic resonance response under an applied radiofrequency. Scanning tunneling microscopes (STM) are commonly used to manipulate, probe and engineer these atomic-scale magnets.

Quite often these systems are described by means of phenomenological models, with a clear drawback: they lack of predictive character. While ab-initio density functional theory (DFT) calculations usually provides valuable and accurate structural information, the microscopic description of the magnetic properties of single adatoms still comprises a formidable challenge.

Here I present a detail study of the magnetic properties of Fe adatoms atop N on a Cu2N/Cu(100) surface studied by a combination of DFT calculations and a multiobital Hubbard model derived from the former. This model, in combination with a cotunneling description of the tunneling current, permits analyzing the spin dynamics and it yields the dI/dV spectrum directly observed experimentally by STM. The method not only accounts for the observed spin excitations, but also for the first observation of a pure orbital moment excitation in an adatom.