Synthesis, structural characterization and magnetic properties of RE2MgGe2 (RE=rare-earth metal)

A series of rare-earth metal–magnesium–germanides RE2MgGe2 (RE=Y, Nd, Sm, Gd–Tm, Lu) has been synthesized by reactions of the corresponding elements at high temperature. Their structures have been established by single-crystal and powder X-ray diffraction and belong to the Mo2FeB2 structure type (space group P4/mbm (No. 127), Z=2; Pearson symbol tP10). Temperature dependent DC magnetization measurements indicate Curie–Weiss paramagnetism in the high-temperature regime for all members of the family, excluding Y2MgGe2, Sm2MgGe2, and Lu2MgGe2. At cryogenic temperatures (ca. 60 K and below), most RE2MgGe2 phases enter into an antiferromagnetic ground-state, except for Er2MgGe2 and Tm2MgGe2, which do not undergo magnetic ordering down to 5 K. The structural variations as a function of the decreasing size of the rare-earth metals, following the lanthanide contraction, and the changes in the magnetic properties across the series are discussed as well.

Graphical AbstractThe structure of RE2MgGe2 (RE=Y, Nd, Sm, Gd–Tm, Lu) can be best viewed as 2-dimensional slabs of Mg and Ge atoms (anionic sub-lattice), and layers of rare-earth metal atoms (cationic sub-lattice) between them. Within this description, one should consider the Ge–Ge dumbbells (formally Ge6−2), interconnected with square-planar Mg atom as forming flat [MgGe2] layers (z=0), stacked along the c-axis with the layers at z=1/2, made of rare-earth metal cations (formally RE3+).Figure optionsDownload as PowerPoint slideHighlights
► RE2MgGe2 (RE=Y, Nd, Sm, Gd–Tm, Lu) are new ternary germanides.
► Their structures can be recognized as a 1:1 intergrowth of CsCl- and AlB2-like slabs.
► Ge atoms are covalently bound into Ge2 dumbbells.
► Most RE2MgGe2 phases are antiferromagnetically ordered at cryogenic temperatures.