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Segregation of calcium and magnesium into different substructures. Ca4Ag0.948Mg and other compounds with Gd4RhIn-type structure

hal.structure.identifierInstitut für Anorganische und Analytische Chemie
dc.contributor.authorKERSTING, Marcel
hal.structure.identifierInstitut de Chimie de la Matière Condensée de Bordeaux [ICMCB]
dc.contributor.authorMATAR, Samir F.
hal.structure.identifierInstitut für Anorganische und Analytische Chemie
dc.contributor.authorSCHWICKERT, Christian
hal.structure.identifierInstitut für Anorganische und Analytische Chemie
dc.contributor.authorPÖTTGEN, Rainer
dc.date.issued2012
dc.identifier.issn0932-0776
dc.description.abstractEnThe metal-rich compounds R4PdMg (R = Ca, Eu, Tb-Lu), R4AgMg (R = Ca, Yb), R4PtMg (R = Eu, Tb-Lu), and R4AuMg (R = Ca, Eu, Yb) were synthesized by induction melting of the elements in sealed tantalum tubes in a water-cooled sample chamber. All samples were characterized bypo wder X-rayd iffraction. The structures of Ca4Ag0.948Mg and Yb4PdMg were refined on the basis of single-crystal X-ray diffractometer data: Gd4RhIn type, F ¯43m, a = 1434.6(1) pm, wR2 = 0.0269, 523 F2 values, 18 variables for Yb4PdMg and a = 1485.78(7) pm, wR2 = 0.0188, 617 F2 values, 20 variables for Ca4Ag0.948Mg. For the first time small defects on the 16e transition metal site of a Gd4RhIn-type compound have been observed, and the first compounds of this structure type with the divalent rare earth elements europium and ytterbium as well as with calcium are reported. The striking structural motif of these compounds (exemplaryf or Ca4Ag0.948Mg) is the clear segregation of two alkaline earth elements into two different substructures, calcium forming trigonal prisms around the silver atoms and magnesium forming covalentlybonded tetrahedra (Mg-Mg 328 pm). The latter are embedded in larger cavities of the adamantane-like three-dimensional network of edge- and corner-sharing AgCa6 trigonal prisms. This is evident from the chemical bonding analysis of the electronic structure by ab initio calculations. The densityof states shows s-like metallic conductivitywith an active role played by the Ag d states within the valence band and for the bonding with calcium. Temperature-dependent magnetic susceptibilityd ata of Eu4PdMg and Eu4PtMg show Curie-Weiss behavior above 230 K with experimental magnetic moments of 7.94(1) and 8.00(1) μB per Eu atom for the palladium and platinum compound, respectively. Ferromagnetic ordering is detected at the comparativelyhi gh Curie temperatures of 150.1(5) (Eu4PdMg) and 139.1(5) (Eu4PtMg) K. Magnetization measurements at 3 K show full parallel spin alignment and the typical behavior of soft ferromagnets.
dc.language.isoen
dc.publisherVerlag der Zeitschrift Fuer Naturforschung
dc.rights.urihttp://creativecommons.org/licenses/by-nc-nd/
dc.subject.enCrystal Structure
dc.subject.enAlkaline earth metals
dc.subject.enMagnesium
dc.subject.enFerromagnetic ordering
dc.title.enSegregation of calcium and magnesium into different substructures. Ca4Ag0.948Mg and other compounds with Gd4RhIn-type structure
dc.typeArticle de revue
dc.identifier.doi10.1515/znb-2012-0111
dc.subject.halChimie/Matériaux
bordeaux.journalZeitschrift fur Naturforschung B
bordeaux.page61-69
bordeaux.volume67
bordeaux.issue1
bordeaux.peerReviewedoui
hal.identifierhal-00673265
hal.version1
hal.popularnon
hal.audienceInternationale
hal.origin.linkhttps://hal.archives-ouvertes.fr//hal-00673265v1
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