Structural and magnetic properties of transition metal substituted BaFe<sub>2</sub>As<sub>2</sub> compounds studied by x-ray and neutron scattering

dc.contributor.advisor Alan I. Goldman
dc.contributor.advisor Andreas Kreyssig
dc.contributor.author Kim, Min Gyu
dc.contributor.department Physics and Astronomy
dc.date 2018-08-12T01:51:48.000
dc.date.accessioned 2020-06-30T02:46:19Z
dc.date.available 2020-06-30T02:46:19Z
dc.date.copyright Sun Jan 01 00:00:00 UTC 2012
dc.date.embargo 2013-06-05
dc.date.issued 2012-01-01
dc.description.abstract <p>The purpose of my dissertation is to understand the structural and magnetic properties of the newly discovered FeAs-based superconductors and the interconnection between superconductivity, antiferromagnetism, and structure. X-ray and neutron scattering techniques are powerful tools to directly observe the structure and magnetism in this system: High-resolution x-ray diffraction, x-ray resonant magnetic scattering, and neutron diffraction measurements have been used. I found that the structural and antiferromagnetic transitions are split in the parent BaFe<sub>2</sub>As<sub>2</sub> compound with second-order structural transition temperature (<em>T</em><sub>S</sub>) higher than the first-order AFM transition temperature (<em>T</em><sub>N</sub>). Upon substitutions by Co and Rh, which are considered as electron doping, the structural and AFM transition temperatures are suppressed to lower temperature and split further. In contrast to the electron doping, in isoelectronic Ru substitution, the structural and AFM transitions are locked at the same temperature while in the hole doping case, the Mn substitution, the <em>T</em><sub>S</sub> and <em>T</em><sub>N</sub> occur at the same temperature up to approximately x = 0.102. Above x ≥ 0.11, the orthorhombic distortion is not observed while the AFM signal from the antiferromagnetic propagation vector <strong>Q</strong><sub>AFM</sub> of the “stripe” AFM structure remains. X-ray resonant magnetic scattering measurements at the Fe <em>K</em> edge add another example of resonance enhancement at the <em>K</em> edge of 3<em>d</em> element (in this case Fe) and definitely show that no incommensurate magnetic ordering exists in ≤ 5.4% Co substituted BaFe<sub>2</sub>As<sub>2</sub> compounds. Neutron diffraction measurements show that the commensurate-to-incommensurate transition occurs in ≥ 5.6% Co substitution, ≥ 3.5% Ni substitution, but not in any level of Cu substitution. I show that simple electron counting based on rigid-band concepts is invalid. These results suggest that substitutional impurity effects in the Fe plane play a significant role in controlling magnetism and the appearance of superconductivity, with Cu distinguished by enhanced impurity scattering and split-band behavior.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/12952/
dc.identifier.articleid 3959
dc.identifier.contextkey 4188284
dc.identifier.doi https://doi.org/10.31274/etd-180810-2639
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/12952
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/27141
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/12952/Kim_iastate_0097E_13065.pdf|||Fri Jan 14 19:33:59 UTC 2022
dc.subject.disciplines Condensed Matter Physics
dc.subject.keywords FeAs based superconductors
dc.subject.keywords Fe K edge resonance
dc.subject.keywords impurity scattering
dc.subject.keywords incommensurate antiferromagnetism
dc.subject.keywords iron pnictide
dc.subject.keywords phase transitions
dc.title Structural and magnetic properties of transition metal substituted BaFe<sub>2</sub>As<sub>2</sub> compounds studied by x-ray and neutron scattering
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication 4a05cd4d-8749-4cff-96b1-32eca381d930
thesis.degree.level dissertation
thesis.degree.name Doctor of Philosophy
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