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Title: RFe{sub 2}Mg{sub x}Al{sub 8−x} (R=La–Nd and Sm; x≈0.8): Flux synthesis, structure, magnetic and electrical properties

Single crystals of Mg-substituted CeFe{sub 2}Al{sub 8} type intermetallics RFe{sub 2}Mg{sub x}Al{sub 8–x} (R=La–Nd and Sm; x≤1) were grown by reacting iron and rare earth metals in 1:1 Mg/Al mixed flux. The structure features mono-capped and bi-capped trigonal prismatic FeAl{sub 6} units. Electronic structure calculations indicate that magnesium substitution reduces the valence electron count, shifting the Fermi level away from a pseudo-gap. This changes the electronic nature of the cerium analog; the previously reported ternary CeFe{sub 2}Al{sub 8} shows strong hybridization between the cerium states and the conduction electrons, resulting in no magnetic moment on Ce atoms. On the other hand, magnetic susceptibility measurements on CeFe{sub 2}Mg{sub x}Al{sub 8–x} indicates a localized moment on cerium. The newly synthesized Pr, Nd and Sm analogs exhibit antiferromagnetic ordering at 2.8 K, 7.8 K and 12 K respectively. Solid state {sup 27}Al NMR of LaFe{sub 2}Mg{sub x}Al{sub 8–x} exhibits a broad Knight shift at ~1200 ppm, consistent with the metallic behavior shown by electrical resistivity data. - Graphical abstract: Mg substitution into CeFe{sub 2}Al{sub 8} modifies cerium valence due to changing valence electron count. - Highlights: • RFe{sub 2}Mg{sub x}Al{sub 8−x} (R=La–Nd, Sm) grow as large crystals from reactions in Mg/Al flux. •more » Products are magnesium-substituted variants of CeFe{sub 2}Al{sub 8}, with CaCo{sub 2}Al{sub 8} structure. • Ce magnetic moment in CeFe{sub 2}Mg{sub x}Al{sub 8−x} varies from that in CeFe{sub 2}Al{sub 8} due to VEC change. • Antiferromagnetic ordering observed for Pr, Nd, Sm analogs of RFe{sub 2}Mg{sub x}Al{sub 8−x}.« less
Authors:
; ;  [1] ;  [2] ;  [1]
  1. Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306 (United States)
  2. Department of Physics, Florida State University, Tallahassee, FL 32306 (United States)
Publication Date:
OSTI Identifier:
22486763
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 229; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALUMINIUM; ALUMINIUM 27; ANTIFERROMAGNETISM; CERIUM; ELECTRIC CONDUCTIVITY; ELECTRONIC STRUCTURE; ELECTRONS; FERMI LEVEL; FLUX SYNTHESIS; INTERMETALLIC COMPOUNDS; IRON; KNIGHT SHIFT; MAGNESIUM; MAGNETIC MOMENTS; MAGNETIC SUSCEPTIBILITY; MONOCRYSTALS; NUCLEAR MAGNETIC RESONANCE; SOLIDS; VALENCE