Symmetry-Breaking Transitions in SmCu1+δAs2—χPχ(δ = 0 — 0.2, χ = 0 — 2). Effect of P and Additional Cu Atoms on Crystal Structures and Magnetic Properties
✍ Scribed by Yurij Mozharivskyj; Alexandra O. Pecharsky; Sergej Bud'ko; Hugo F. Franzen
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- German
- Weight
- 416 KB
- Volume
- 628
- Category
- Article
- ISSN
- 0372-7874
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✦ Synopsis
Crystal structures of the compounds SmCu 1ϩδ As 2Ϫx P x (δ ϭ 0 Ϫ 0.2, x ϭ 0 Ϫ 2) undergoing symmetry-breaking transitions and SmCuP 2.3 have been investigated by the X-ray single crystal and powder methods. While the phases SmCuAs 2 through SmCu-As 1.22 P 0.78 retain the tetragonal HfCuSi 2 structure (P4/nmm space group), the compounds SmCuAs 1.11 P 0.89 through SmCuAs 0.56 P 1.44 adopt the GdCuAs 1.15 P 0.85 Ϫtype structure (Pmmn space group), an orthorhombic variant of the HfCuSi 2 -type. Further distortion follows in SmCuAs 0.33 P 1.67 through SmCuP 2.3 , the powder patterns of which were indexed in the P2/n space group (P2/c in a standard setting). According to Landau theory the transitions from tetragonal SmCuAs 1.22 P 0.78 to orthorhombic SmCuAs 1.11 P 0.89 and from orthorhombic SmCuAs 0.56 P 1.44 to monoclinic SmCuAs 0.33 P 1.67 can be continuous. Introducing extra copper into some of the orthorhombic arsenophosphides restabilizes tetragonal phases (0 < δ Յ 0.2) with the P4/nmm symmetry, and the reverse transition Pmmn Ǟ P4/nmm can be continuous. Inserting copper atoms into mono-Symmetrieerniedrigende Phasenumwandlungen in SmCu 1؉δ As 2؊x P x (δ ؍ 0 ؊ 0,2, x ؍ 0 ؊ 2). Der Einfluß von P-und zusätzlichen Cu-Atomen auf die Kristallstrukturen und magnetische Eigenschaften Inhaltsübersicht. Die Kristallstrukturen der Verbindungen SmCu 1ϩδ As 2Ϫx P x (δ ϭ 0 Ϫ 0,2, x ϭ 0 Ϫ 2), die symmetrieerniedrigende Phasenumwandlungen eingehen, und von SmCuP 2,3 wurden durch Röntgen-Einkristall-und -Pulver-Methoden untersucht. Während bei SmCuAs 2 bis SmCuAs 1,22 P 0,78 die tetragonale HfCuSi 2 -Struktur erhalten bleibt (Raumgruppe P4/nmm), nehmen