Degree Type

Dissertation

Date of Award

2001

Degree Name

Doctor of Philosophy

Department

Physics and Astronomy

First Advisor

David W. Lynch

Abstract

Fe2VAl has recently been discovered to have a negative temperature coefficient of resistivity, moderately enhanced specific heat coefficient, and a large DOS at the Fermi level by photoemission. This triggered a round of heated research to understand the ground state of this material, both theoretically and experimentally. Here we report a comprehensive characterization of Fe2VAl. X-ray diffraction exhibited appreciable antisite disorder in all of our samples. FTIR spectroscopy measurements showed that the carrier density and scattering time had little sample-to-sample variation or temperature dependence for near-stoichiometric samples. FTIR and DC resistivity suggest that the transport properties of Fe2VAl are influenced by both localized and delocalized carriers, with the former primarily responsible for the negative temperature coefficient of resistivity. Magnetization measurements reveal that near-stoichiometric samples have superparamagnetic clusters with at least two sizes of moments. X-ray photoemission from Fe core level shows localized magnetic moments on site-exchanged Fe. We conclude that in Fe 2VAl, antisite disorder causes significant modification to the semi-metallic band structure proposed by LDA calculations. With antisite disorder considered, we are now able to explain most of the physical properties of Fe2VAl.

DOI

https://doi.org/10.31274/rtd-180813-10959

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

Ye Feng

Language

en

Proquest ID

AAI3003241

File Format

application/pdf

File Size

63 pages

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