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.
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Host: Williams
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