Condensed Matter Physics Seminar

2 p.m., Thursday, February 22, 2006
Room 1201, Physics Building

 Magnetic Nanostructures Probed on the Atomic Scale

Cyrus F. Hirjibehedin

(IBM Almaden Research Center)

Abstract:  Magnetic nanostructures are increasing data storage capacities and are promising candidates for implementations of novel spin-based computation techniques. The relative simplicity and reduced dimensionality of nanoscale magnetic structures also make them attractive model systems for studying fundamental interactions between quantum spins. We used a scanning tunneling microscope to probe the interactions between spins in individual atomic-scale magnetic structures. Linear chains of 1 to 10 Mn atoms were assembled one atom at a time on a thin decoupling layer of copper nitride on bare copper. The spin excitation spectra of these structures were measured with inelastic electron tunneling spectroscopy. We observed excitations of the coupled atomic spins that can change both the total spin and its orientation. Comparison with a model spin interaction Hamiltonian yielded the collective spin configuration and the strength of the exchange coupling between the atomic spins. Anisotropy effects were directly manifested in the excitation spectra as finite energy excitations in the absence of a magnetic field. The effects of anisotropy were found to be relatively weak for Mn atoms but were substantially larger in atoms with strong spin-orbit coupling, such as Fe.
Host:  Williams
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