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.