Investigation of a d-electron Kondo insulator FeSb2.
Degree: PhD, Physics, 2009, Brown University
FeSb2 is a narrow band semiconductor, whose magnetic
susceptibility strongly resembles that of FeSi, an archetype
example of Kondo insulator. The unusual spectral weight transfer in
the optical conductivity measurement and ab initio LDA+U
calculations imply that FeSb2 is an unconventional semiconductor
with strong electron correlations. In order to study the anisotropy
and probe the electronic structure of FeSb2, single crystals are
grown by high temperature flux method and carriers are introduced
into FeSb2 by substituting Fe and Sb with Co/Cr and Te
respectively. We investigated the magnetic and electrical
properties of FeSb2 and the doping effects. Hall measurement on
FeSb2 reveals that multiple band carriers with very large mobility
difference are involved in the electrical transport. This can be
explained by the orbital selective hybridization of the Fe
d-orbitals with Sb-p electrons in FeSb2 involving only one
electronic subsystem. Band structure calculation suggests that
FeSb2 is close to a magnetic instability. Indeed, various magnetic
orders are experimentally observed in doped FeSb2. For example, the
activated Pauli paramagnetism of FeSb2 evolves into a weak
ferromagnetism in Fe1-xCoxSb2 and a complex canted
antiferromagnetic structure in Fe1-xCrxSb2 and Fe(Sb1-xTex)2.
Metallic states are readily induced by doping FeSb2 as a result of
band filling. Positive colossal magnetoresistance mainly attributed
to quasi 1D weak localization is observed in Co doped FeSb2. With
Te substitution, FeSb2 evolves from a strongly correlated
semiconductor into a moderate heavy fermion metal. Most of the
Kondo insulator materials are cubic, with the exception of CeRhSb
and CeNiSn, and 4f intermetallics. An important question is that if
the Kondo insulator scenario can be applied to 3d materials, e.g.
FeSi and FeSb2. FeSb2 can be obtained in single crystal form with
high quality and can be readily doped with carriers, thus it
represents a model system with only 3d elements to study this
physics. Our results indicate that the underling physics of FeSb2
can be well described by the Kondo insulator picture and FeSb2
resembles FeSi in many ways as a prototypical example of a
nonrare-earth containing Kondo insulator.
Advisors/Committee Members: Mitrovic, Vesna (director), Petrovic, Cedomir (director), Marston, Brad (reader), Valles, James (reader).
Subjects/Keywords: Kondo Insulator
to Zotero / EndNote / Reference
APA (6th Edition):
Hu, R. (2009). Investigation of a d-electron Kondo insulator FeSb2. (Doctoral Dissertation). Brown University. Retrieved from https://repository.library.brown.edu/studio/item/bdr:185/
Chicago Manual of Style (16th Edition):
Hu, Rongwei. “Investigation of a d-electron Kondo insulator FeSb2.” 2009. Doctoral Dissertation, Brown University. Accessed January 26, 2021.
MLA Handbook (7th Edition):
Hu, Rongwei. “Investigation of a d-electron Kondo insulator FeSb2.” 2009. Web. 26 Jan 2021.
Hu R. Investigation of a d-electron Kondo insulator FeSb2. [Internet] [Doctoral dissertation]. Brown University; 2009. [cited 2021 Jan 26].
Available from: https://repository.library.brown.edu/studio/item/bdr:185/.
Council of Science Editors:
Hu R. Investigation of a d-electron Kondo insulator FeSb2. [Doctoral Dissertation]. Brown University; 2009. Available from: https://repository.library.brown.edu/studio/item/bdr:185/