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http://doi.org/10.25358/openscience-3369Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor.author | Kandpal, Hem Chandra | |
| dc.date.accessioned | 2007-09-25T10:28:10Z | |
| dc.date.available | 2007-09-25T12:28:10Z | |
| dc.date.issued | 2007 | |
| dc.identifier.uri | https://openscience.ub.uni-mainz.de/handle/20.500.12030/3371 | - |
| dc.description.abstract | The purpose of this thesis is to further the understanding of the structural, electronic and magnetic properties of ternary inter-metallic compounds using density functional theory (DFT). Four main problems are addressed. First, a detailed analysis on the ternary Heusler compounds is made. It has long been known that many Heusler compounds ($X_2YZ$; $X$ and $Y$ transition elements, $Z$ main group element) exhibit interesting half-metallic and ferromagnetic properties. In order to understand these, the dependence of magnetic and electronic properties on the structural parameters, the type of exchange-correlation functional and electron-electron correlation was examined. It was found that almost all Co$_2YZ$ Heusler compounds exhibit half-metallic ferromagnetism. It is also observed that $X$ and $Y$ atoms mainly contribute to the total magnetic moment. The magnitude of the total magnetic moment is determined only indirectly by the nature of $Z$ atoms, and shows a trend consistent with Slater-Pauling behaviour in several classes of these compounds. In contrast to experiments, calculations give a non-integer value of the magnetic moment in certain Co$_2$-based Heusler compounds. To explain deviations of the calculated magnetic moment, the LDA+$U$ scheme was applied and it was found that the inclusion of electron-electron correlation beyond the LSDA and GGA is necessary to obtain theoretical description of some Heusler compounds that are half-metallic ferromagnets. The electronic structure and magnetic properties of substitutional series of the quaternary Heusler compound Co$_2$Mn$_{1-x}$Fe$_x$Si were investigated under LDA+$U$. The calculated band structure suggest that the most stable compound in a half-metallic state will occur at an intermediate Fe concentration. These calculated findings are qualitatively confirmed by experimental studies. Second, the effect of antisite disordering in the Co$_2$TiSn system was investigated theoretically as well as experimentally. Preservation of half-metallicity for Co$_2$TiSn was observed with moderate antisite disordering and experimental findings suggest that the Co and Ti antisites disorder amounts to approximately 10~\% in the compound. Third, a systematic examination was carried out for band gaps and the nature (covalent or ionic) of bonding in semiconducting 8- and 18-electron or half-metallic ferromagnet half-Heusler compounds. It was found that the most appropriate description of these compounds from the viewpoint of electronic structures is one of a $YZ$ zinc blende lattice stuffed by the $X$ ion. Simple valence rules are obeyed for bonding in the 8- and 18-electron compounds. Fourth, hexagonal analogues of half-Heusler compounds have been searched. Three series of compounds were investigated: GdPdSb, GdAu\textit{X} (\textit{X} = Mn, Cd and In) and EuNiP. GdPdSb is suggested as a possible half- metallic weak ferromagnet at low temperature. GdAu\textit{X} (\textit{X} = Mn, Cd and In) and EuNiP were investigated because they exhibit interesting bonding, structural and magnetic properties. The results qualitatively confirm experimental studies on magnetic and structural behaviour in GdPdSb, GdAu\textit{X} (\textit{X} = Mn, Cd and In) and EuNiP compounds. ~ | en_GB |
| dc.language.iso | eng | |
| dc.rights | InCopyright | de_DE |
| dc.rights.uri | https://rightsstatements.org/vocab/InC/1.0/ | |
| dc.subject.ddc | 540 Chemie | de_DE |
| dc.subject.ddc | 540 Chemistry and allied sciences | en_GB |
| dc.title | Computational studies on the structure and stabilities of magnetic inter-metallic compounds | en_GB |
| dc.type | Dissertation | de_DE |
| dc.identifier.urn | urn:nbn:de:hebis:77-13603 | |
| dc.identifier.doi | http://doi.org/10.25358/openscience-3369 | - |
| jgu.type.dinitype | doctoralThesis | |
| jgu.type.version | Original work | en_GB |
| jgu.type.resource | Text | |
| jgu.organisation.department | FB 09 Chemie, Pharmazie u. Geowissensch. | - |
| jgu.organisation.year | 2007 | |
| jgu.organisation.number | 7950 | - |
| jgu.organisation.name | Johannes Gutenberg-Universität Mainz | - |
| jgu.rights.accessrights | openAccess | - |
| jgu.organisation.place | Mainz | - |
| jgu.subject.ddccode | 540 | |
| opus.date.accessioned | 2007-09-25T10:28:10Z | |
| opus.date.modified | 2007-09-25T10:28:10Z | |
| opus.date.available | 2007-09-25T12:28:10 | |
| opus.subject.other | Inter-metallic, Heusler, Half-metallic ferromagnets | en_GB |
| opus.organisation.string | FB 09: Chemie, Pharmazie und Geowissenschaften: FB 09: Chemie, Pharmazie und Geowissenschaften | de_DE |
| opus.identifier.opusid | 1360 | |
| opus.institute.number | 0900 | |
| opus.metadataonly | false | |
| opus.type.contenttype | Dissertation | de_DE |
| opus.type.contenttype | Dissertation | en_GB |
| jgu.organisation.ror | https://ror.org/023b0x485 | |
| Appears in collections: | JGU-Publikationen | |
