Dr. Tom Giebultowiczs research

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Dr. Tom Giebultowiczs research

• My pricipal research tool is elastic and
  inelastic
• neutron scattering. These methods are particu-
• larly useful for studying magnetism in solids.
• Our research is focused on magnetic semicon-
• ductors, and on thin (very thin!) film structures
• made of these materials (such as, e.g., super-
• lattices consisting of alternating layers of
• magnetic and non-magnetic semiconductors).

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NIST Center for Neutron Research
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The 20 MW NIST Research Reactor
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This is one of the instruments I use
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Why are magnetic thin films interesting and
important?

• Well, for many reasons. For instance, some
  magnetic thin film systems exhibit an effect
  called Giant Magnetoresistance (GMR). It has
  important practical applications (e.g., in
  reading heads of computer hard drives). The two
  gentlemen who discovered GMR in 1988 were awarded
  the 2007 Nobel Prize in Physics for that.

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2007 Nobel Prize in Physics discovery of Giant
Magnetoresistance (GMR)
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More spin valves
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Ferromagnetic EuS/PbS and EuS/YbSe SLs
EuS Heisenberg ferromagnet TC 16.6 K (bulk),
Eg1.5 eV PbS narrow-gap (Eg0.3 eV)
semiconductor (n 1017 cm-3) YbSe wide-gap
(Eg1.6 eV) semiconductor (semiinsulator) all
NaCl-type structure with lattice constants 5.968
? 5.936 ? 5.932 ? (lattice mismatch 0.5)
4-200 ?
30-60 Å
number of repetitions 10-20
(001) a6.29 Å
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Unpolarized neutron reflectivity experiments on
the EuS/PbS system (NG-1 reflectometer, NIST
Center for Neutron Research)
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On-campus work

• We do computer simulation studies related to our
  experimental work performed at NIST.
• Occasionally, we organize tours to NIST for
  undergraduate students, but we cannot arrange
  visits long enough that would allow them to make
  their senior thesis research over there. However,
  there is much interesting computer simulation
  stuff that undergrads may do in our group!
  Undergrads are always welcome in our lab!