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Magnetism in Giant Unit Cells – Crystal Structure and Magnetic Properties of R 117 Co 52+ δ Sn 112+ γ (R = Sm, Tb, Dy)
Author(s) -
Kovnir Kirill,
Shatruk Michael
Publication year - 2011
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201100200
Subject(s) - crystallography , chemistry , magnetism , paramagnetism , crystal structure , ferromagnetism , intermetallic , antiferromagnetism , polyhedron , vertex (graph theory) , ternary operation , alloy , condensed matter physics , physics , geometry , combinatorics , graph , mathematics , organic chemistry , computer science , programming language
Ternary polar intermetallics Sm 117 Co 55.6 Sn 116 , Tb 117 Co 59 Sn 111 , and Dy 117 Co 58 Sn 111 were prepared by the arc‐melting technique. They belong to the Tb 117 Fe 52 Ge 112 structure type and are characterized by a giant cubic unit cell ( V > 25000 Å 3 ). The build‐up of the structure can be understood by identifying three basic metal‐centered polyhedra, a 14‐vertex Co@Co 6 Sn 8 at the edge centers and at the body center of the unit cell, a 14‐vertex Sm@Co 8 Sn 6 at the origin of the unit cell, and a 22‐vertex Sm@Co 12 Sn 10 at the center of each octant. The rest of the atoms in the crystal structure can be considered as forming concentric polyhedra around these basic units. Such an approach results in three types of large multishell polyhedra that share their outermost faces and provide complete space filling. The arrangement of these polyhedra follows the arrangement of atoms in the structure of Heusler alloy Cu 2 MnAl. The description of this complex structure in terms of multishell clusters allows its separation into regions of different polarity, as each individual shell is composed of either Sm or Co/Sn atoms. Sm 117 Co 55.6 Sn 116 exhibits ferromagnetic ordering in the Sm sublattice at 86 K. Tb 117 Co 59 Sn 111 and Dy 117 Co 58 Sn 111 undergo consecutive paramagnet–ferromagnet and ferromagnet‐canted–antiferromagnet phase transitions when the temperature is lowered. The transitions take place at 38 K and 20 K for Tb 117 Co 59 Sn 111 and at 30 K and 11 K for Dy 117 Co 58 Sn 111 .