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SUMMARY:Spin-Excitation Spectroscopy: Probing Magnetic Nanostructures at t
 he Atomic Scale - Cyrus Hirjibehedin\, University College London
DTSTART:20090225T111500Z
DTEND:20090225T121500Z
UID:TALK15082@talks.cam.ac.uk
CONTACT:Michael Sutherland
DESCRIPTION:The spectroscopic capabilities of a scanning tunneling microsc
 ope (STM) can be used to measure the low energy excitation spectrum of ind
 ividual nanostructures on surfaces with atomic-scale detail. Originally us
 ed to probe the vibrations of single molecules\, inelastic\nelectron tunne
 ling spectroscopy can also measure magnetic excitations.  We discuss recen
 t studies in which we have used STM-based spin-excitation spectroscopy to 
 determine the orientation and\nstrength of the anisotropies for individual
  atomic spins on a copper nitride surface\, as well as the interplay betwe
 en magnetic anisotropy and Kondo screening.  In structures containing more
  than one magnetic atom\, we observe excitations of the coupled spin syste
 m that can change both the total spin and its orientation.  We are able to
  describe the mechanisms that drive these inelastic spin excitations using
  a simple exchange coupling between the tunneling electron and the electro
 ns that comprise the atomic spin.  This description predicts the existence
  of a sum rule that includes a previously unnoticed type of spin-dependent
  elastic scattering\, and evidence of both are seen in the observed spectr
 a. We discuss the key factors that\ndetermine the relative strength of the
  inelastic tunneling\, providing insight on when such processes can be obs
 erved and potentially how they might be enhanced.\n
LOCATION:Mott Seminar Room\, Cavendish Laboratory\, Department of Physics
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