Electronic structure, magnetic structure, and metal-atom site preferences in CrMnAs

dc.contributor.advisor Gordon J. Miller
dc.contributor.advisor Scott Beckman
dc.contributor.author Lutz, Laura
dc.contributor.department Materials Science and Engineering
dc.date 2018-08-11T12:59:40.000
dc.date.accessioned 2020-06-30T02:48:33Z
dc.date.available 2020-06-30T02:48:33Z
dc.date.copyright Tue Jan 01 00:00:00 UTC 2013
dc.date.embargo 2015-07-30
dc.date.issued 2013-01-01
dc.description.abstract <p>Density functional theory was used to examine stoichiometric CrMnAs, one of a class of 3d-metal arsenides that exhibit cooperative magnetic ordering. CrMnAs is a tetragonal structure with two inequivalent metal sites: M(I), which is tetrahedral coordinate, and M(II), which is square pyramidal coordinate. CrMnAs thus presents a “coloring problem,” the question of how the two types of metal atoms are distributed between the two types of metal sites. Previous diffraction studies have determined that CrMnAs is antiferromagnetic with the M(I) site primarily occupied by Cr.</p> <p>TB-LMTO-ASA local density approximation (LDA) calculations showed indications of instability in the nonmagnetic structure, which could be resolved either by structural distortion or by spin polarization. LDA crystal orbital Hamilton population (COHP) curves were used to predict the nature of particular direct-exchange interactions upon spin polarization. Spin-polarized total energy calculations were performed using VASP with the generalized gradient approximation (GGA).</p> <p>The lowest-energy structure had Mn at the M(I) site and a different antiferromagnetic ordering than previously observed. The structure with the second-lowest calculated total energy also had Mn at M(I). Next lowest were four structures with Cr at M(I), including the experimentally observed structure. Those four had calculated total energies ranging from 154.2 to 167.8 meV/f.u. higher than the lowest-energy case. The number of possible structures with small energy differences suggests that the observed magnetic ordering and coloring may be due to entropy rather than reflecting a true electronic ground state.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/13271/
dc.identifier.articleid 4278
dc.identifier.contextkey 4615765
dc.identifier.doi https://doi.org/10.31274/etd-180810-3269
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/13271
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/27460
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/13271/Lutz_iastate_0097M_13609.pdf|||Fri Jan 14 19:48:33 UTC 2022
dc.subject.disciplines Chemistry
dc.subject.disciplines Mechanics of Materials
dc.subject.keywords antiferromagnetism
dc.subject.keywords COHP
dc.subject.keywords cooperative magnetism
dc.subject.keywords CrMnAs
dc.subject.keywords density functional theory
dc.subject.keywords VASP
dc.title Electronic structure, magnetic structure, and metal-atom site preferences in CrMnAs
dc.type article
dc.type.genre thesis
dspace.entity.type Publication
relation.isOrgUnitOfPublication bf9f7e3e-25bd-44d3-b49c-ed98372dee5e
thesis.degree.level thesis
thesis.degree.name Master of Science
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