Investigation of a d-electron Kondo insulator FeSb2

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Date/Time:Thursday, 24 Sep 2009 from 4:10 pm to 5:00 pm
Location:Physics 5
Channel:Condensed Matter Physics
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Rongwei Hu (Ames Laboratory)

FeSb2 is a narrow band semiconductor, whose magnetic susceptibility strongly resembles that of FeSi, an archetype example of a 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. Band structure calculation suggests that FeSb2 is close to a magnetic instability. Indeed, and various magnetic orders are experimentally observed in doped FeSb2. 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.