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Trivalent‐Intermediate Valent Cerium Ordering in CeRuSn – A Static Intermediate Valent Cerium Compound with a Superstructure of the CeCoAl Type
Author(s) -
Riecken Jan F.,
Hermes Wilfried,
Chevalier Bernard,
Hoffmann RolfDieter,
Schappacher Falko M.,
Pöttgen Rainer
Publication year - 2007
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200700066
Subject(s) - superstructure , cerium , monoclinic crystal system , crystallography , crystal structure , materials science , single crystal , magnetic susceptibility , chemistry , inorganic chemistry , physics , thermodynamics
New equiatomic stannide CeRuSn was synthesized from the elements by arc‐melting. CeRuSn was investigated by X‐ray powder and single crystal diffraction: C 2/ m , a = 1156.1(4), b = 475.9(2) and c = 1023.3(4) pm, β = 102.89(3)°, wR2 = 0.0466, 1229 F 2 values and 38 variables. CeRuSn adopts a superstructure of the monoclinic CeCoAl type through a doubling of the subcell c axis. In the superstructure two crystallographically independent cerium sites occur. Based on the interatomic distances the two sites can be assigned to trivalent Ce2 and intermediate valent Ce1. This trivalent‐intermediate valent cerium ordering is underlined by magnetic susceptibility measurements χ m (T): below 150 K χ m , measured with decreasing temperature, follows a Curie‐Weiss law χ m = C m /(T–θ p ) giving C m = 0.38 emuK/mol as Curie constant per CeRuSn mol; a value showing that only half of the cerium atoms are trivalent in CeRuSn (C m = 0.807 emuK/mol for one free Ce 3+ ion). A remarkable feature of the CeRuSn structure are the short Ce1–Ru1 (233 pm) and Ce1–Ru2 (246 pm) distances. The crystal chemistry of CeRuSn is discussed on the basis of a group‐subgroup scheme.