Closely Related Rare-Earth Metal Germanides <i>RE</i>₂Li₂Ge₃ and <i>RE</i>₃Li₄Ge₄ (<i>RE</i> = La–Nd, Sm): Synthesis, Crystal Chemistry, and Magnetic Properties

Reported are the syntheses, crystal structures, and magnetic susceptibilities of two series of closely related rare-earth metal–lithium germanides <i>RE</i>₂Li₂Ge₃ and <i>RE</i>₃Li₄Ge₄ (<i>RE </i>= La–Nd, Sm). All title compounds have been synthesized by reactions of the corresponding elements at high temperatures, and their structures have been established by single-crystal X-ray diffraction. <i>RE</i>₂Li₂Ge₃ phases crystallize in the orthorhombic space group <i>Cmcm</i> (No. 63) with the Ce₂Li₂Ge₃ structure type, while the <i>RE</i>₃Li₄Ge₄ phases crystallize in the orthorhombic space group <i>Immm</i> (No. 71) with the Zr₃Cu₄Si₄ structure type, respectively. Both of their structures can be recognized as the intergrowths of MgAl₂Cu- and AlB₂-like slabs, and these traits of the crystal chemistry are discussed. Temperature-dependent direct-current magnetization measurements indicate Curie–Weiss paramagnetism in the high-temperature regime for <i>RE</i>₂Li₂Ge₃ and <i>RE</i>₃Li₄Ge₄ (<i>RE </i>= Ce, Pr, Nd), while Sm₂Li₂Ge₃ and Sm₃Li₄Ge₄ exhibit Van Vleck-type paramagnetism. The data are consistent with the local-moment magnetism expected for <i>RE</i>³⁺ ground states. At temperatures below ca. 20 K, magnetic ordering transitions have been observed. The experimental results have been complemented by tight-binding linear muffin-tin orbital electronic-band-structure calculations