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Ab Initio Structure Evaluation of Aperiodic Structures in the Rare Earth – Ruthenium Systems

Carlsson, Alfred LU (2015) KOO920 20151
Centre for Analysis and Synthesis
Abstract
Binary alloys comprising of the rare earth metals along with ruthenium, RE-Ru, have been noted to display superconductivity at low temperatures. Furthermore the alloys display interesting magnetic properties such as anomalies in magnetization measurements below the magnetic ordering temperature. In order to understand how some compounds obtain these intrinsic properties it is vital to investigate the crystallography of the compounds. In this thesis the structure, LaRux, of compounds comprising praseodymium, neodymium or lanthanum in the 35-38 at. % Ruthenium region has been investigated with modern x-ray diffraction techniques. Other compounds, Er3Ru2 and Y44Ru25, in the 30-40 at. % Ru region has been noted to show evidence of possible... (More)
Binary alloys comprising of the rare earth metals along with ruthenium, RE-Ru, have been noted to display superconductivity at low temperatures. Furthermore the alloys display interesting magnetic properties such as anomalies in magnetization measurements below the magnetic ordering temperature. In order to understand how some compounds obtain these intrinsic properties it is vital to investigate the crystallography of the compounds. In this thesis the structure, LaRux, of compounds comprising praseodymium, neodymium or lanthanum in the 35-38 at. % Ruthenium region has been investigated with modern x-ray diffraction techniques. Other compounds, Er3Ru2 and Y44Ru25, in the 30-40 at. % Ru region has been noted to show evidence of possible superstructure and has also been examined with x-ray diffraction in order to establish the connection between the two related crystal structures and to fully understand the extent and nature of the structures.
The structure of the incommensurately modulated two composite compound Er3Ru2 was solved using the current (3+1)d superspace approach from structure data which was collected with x-ray single-crystal diffraction. The structure solution, performed with the charge-flipping algorithm, resulted in the non-centrosymmetric super-space group X3 (00γ)0 with a = b = 13.893 (4) Å, c = 4.0005 (12) Å q = 1.572 c*.
The possibility for superstructure descriptions for the Y44Ru25 and the LaRux compounds could also be concluded. The diffraction patterns of both compounds contained satellite reflections, indicating superstructure. Furthermore the Y44Ru25 structure could be solved well with two symmetry incompatible lattices further strengthening the possibility of superstructure. Therefore it could be concluded that these compounds most likely can be well described with the superspace description. The task of describing them in higher-dimensions was not completed in this thesis and is considered future work. (Less)
Abstract (Swedish)
Binära föreningar beståendes av sällsynta jordartsmetallerna och rutenium uppvisar intressanta egenskaper såsom superledande förmåga och intressanta magnetiska egenskaper. För att förstå varför vissa föreningar uppvisar sådana egenskaper är det essentiellt att studera föreningarnas kristallstruktur. I denna rapport undersöks föreningar, i 35-38 at. % Ru regionen, beståendes av praseodym, neodymium eller lantan med hjälp av röntgendiffraktionsanalys. Andra faser i 30-40 at. % Ru, specifikt Er3Ru2 och Y44Ru25, har uppvisat tecken som tyder på att dessa strukturer bättre kan beskrivas i högre dimensioner, s.k. super-rymden. Även dessa föreningar har undersökts med röntgendiffraktionsanalys för att kunna ge en ny beskrivning av dess... (More)
Binära föreningar beståendes av sällsynta jordartsmetallerna och rutenium uppvisar intressanta egenskaper såsom superledande förmåga och intressanta magnetiska egenskaper. För att förstå varför vissa föreningar uppvisar sådana egenskaper är det essentiellt att studera föreningarnas kristallstruktur. I denna rapport undersöks föreningar, i 35-38 at. % Ru regionen, beståendes av praseodym, neodymium eller lantan med hjälp av röntgendiffraktionsanalys. Andra faser i 30-40 at. % Ru, specifikt Er3Ru2 och Y44Ru25, har uppvisat tecken som tyder på att dessa strukturer bättre kan beskrivas i högre dimensioner, s.k. super-rymden. Även dessa föreningar har undersökts med röntgendiffraktionsanalys för att kunna ge en ny beskrivning av dess kristallstruktur.
Strukturen av den inkommensurat modulerade kompositstruktur föreningen Er3Ru2 löstes framgångsrikt med hjälp av den rådande (3+1)d formalismen. Strukturlösningen gjordes med hjälp av programmet Jana2006 som använde data genererad från röntgendiffraktometern. Struktur lösningen resulterande i super-rymdgruppen X3(00γ)0 med cellparametrarna a = b = 13,893 (4) Å, c = 4,0005 (12) Å q = 1,572 c*.
Den högre dimensionella beskrivningen av de två andra föreningarna utfördes inte i detta arbete. Flera indikationer på att dessa föreningar kan beskrivas väl i högre dimensioner kunde dock påvisas. Diffraktionsmönstren för de båda föreningarna visade sig innehålla, förutom huvudreflektioner, satellitreflektioner vilket indikerar en superstruktur. Föreningen bestående av yttrium och rutenium kunde dessutom beskrivas väl av två symmetriinkompatibla gitter vilket är ytterligare en indikation för förekomsten av en superstruktur. (Less)
Popular Abstract
This thesis has answered the question; are the Er3Ru2, Y44Ru25 and LaRux crystal structures aperiodic in three-dimensions and therefore better described in higher dimensions? The short answer to the question above is yes! All three crystal structures can most likely be better described in four dimensions.
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author
Carlsson, Alfred LU
supervisor
organization
course
KOO920 20151
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Crystallography, Higher-Dimensional Crystal Structures, Aperiodic Structures, Er3Ru2, LaRux, Y44Ru25, Superspace, Rare Earth-Ruthenium, Binary Rare Earth-Ruthenium Systems
language
English
id
7512736
date added to LUP
2015-08-18 11:25:51
date last changed
2015-08-18 11:25:51
@misc{7512736,
  abstract     = {Binary alloys comprising of the rare earth metals along with ruthenium, RE-Ru, have been noted to display superconductivity at low temperatures. Furthermore the alloys display interesting magnetic properties such as anomalies in magnetization measurements below the magnetic ordering temperature. In order to understand how some compounds obtain these intrinsic properties it is vital to investigate the crystallography of the compounds. In this thesis the structure, LaRux, of compounds comprising praseodymium, neodymium or lanthanum in the 35-38 at. % Ruthenium region has been investigated with modern x-ray diffraction techniques. Other compounds, Er3Ru2 and Y44Ru25, in the 30-40 at. % Ru region has been noted to show evidence of possible superstructure and has also been examined with x-ray diffraction in order to establish the connection between the two related crystal structures and to fully understand the extent and nature of the structures. 
The structure of the incommensurately modulated two composite compound Er3Ru2 was solved using the current (3+1)d superspace approach from structure data which was collected with x-ray single-crystal diffraction. The structure solution, performed with the charge-flipping algorithm, resulted in the non-centrosymmetric super-space group X3 (00γ)0 with a = b = 13.893 (4) Å, c = 4.0005 (12) Å q = 1.572 c*.
The possibility for superstructure descriptions for the Y44Ru25 and the LaRux compounds could also be concluded. The diffraction patterns of both compounds contained satellite reflections, indicating superstructure. Furthermore the Y44Ru25 structure could be solved well with two symmetry incompatible lattices further strengthening the possibility of superstructure. Therefore it could be concluded that these compounds most likely can be well described with the superspace description. The task of describing them in higher-dimensions was not completed in this thesis and is considered future work.},
  author       = {Carlsson, Alfred},
  keyword      = {Crystallography,Higher-Dimensional Crystal Structures,Aperiodic Structures,Er3Ru2,LaRux,Y44Ru25,Superspace,Rare Earth-Ruthenium,Binary Rare Earth-Ruthenium Systems},
  language     = {eng},
  note         = {Student Paper},
  title        = {Ab Initio Structure Evaluation of Aperiodic Structures in the Rare Earth – Ruthenium Systems},
  year         = {2015},
}