Correlations between Chemical Bonding and Magnetic Exchange Interactions: Synthesis, Crystal Structures, and Magnetic Properties of the New Family RE₂AlGe₂ (RE = Tb–Tm, Lu)

Abstract

Six new rare-earth metal germanides with general formula RE2Al(1-x)Ge(2+x) (RE = Tb-Tm, Lu; 0.13(2) ≤ x ≤ 0.37(2)) have been synthesized by direct fusion of the corresponding elements. Their structures have been established by single-crystal diffraction to crystallize with the orthorhombic space group Immm (no. 74), adopting the W2CoB2 structure type. The Al and Ge atoms are arranged in alternating planar layers, made of rhombic- and hexagonal-fragments. The rare-earth metal substructure consists of puckered four-connected nets. Electronic structure calculations support the coloring of the Ge and Al sites and account for the existence of a small homogeneity range. DC magnetization measurements for all specimens are also presented; based on the RKKY and mean-field theories for antiferromagnets, relationships between the chemical bonding and exchange interactions are discussed.

Structural Modulations in the Rare-Earth Metal Digermanides REAl1–xGe2 (RE = Gd–Tm, Lu, Y; 0.8 < x < 0.9). Correlations between Long- and Short-Range Vacancy Ordering

“…For example, employing Sn afforded the RESnGe family (ZrSi 2 structure type), while the neighboring element In favored a different structural arrangement, as seen for the RE 2 InGe 2 series (Mo 2 FeB 2 structure type) . Drawing on a prior synthetic experience with RE[Al x Si 1– x ] 2 and RE[Ga x Si 1– x ] 2 , we expected similar trends with regard to RE[Al x Ge 1– x ] 2 ; however, the earlier experiments with these elements led to the identification of RE 2 AlGe 2 with the W 2 CoB 2 structure type . At that time, the REAl 1– x Ge 2 phases were obtained as minor products …”

Structural analysis of Gd6FeBi2 from single-crystal X-ray diffraction methods and electronic structure calculations

“…From the above, it appears that in these binary and ternary gadolinium bismuthides, the magnetic interactions correlate with the decrease in Gd-Gd distance. In our previous work on rare-earth metal germanides, whose structures exhibit low magnetic anisotropy, it was found that the RE-RE magnetic-exchange interactions in this class of compounds are a function of the nearest-neighbor distances (Zhang & Bobev, 2013). In the cited paper it was argued that this is the case because the local 4f moments of the RE atoms, at least in the compounds with nonmagnetic elements, generally interact via RKKY-type interactions (Ruderman & Kittel, 1954).…”

Synergistic Geometrical and Electronic Features in the Intermetallic Phases Ca2AgM2, Ca2MgM2, and Ca2GaM2 (M = Pd, Pt)

“…Ca 2 CdM 2 and Ca 2 Cu 2 Ga. [5,22,23] A very detailed renewed description of this structure type can be found in a recent report on the isotypic RE 2 AlGe 2 (RE = rareearth). [6] A projection of the Ca 2 MgPd 2 structure (representative), approximately along the a axis, is illustrated in Figure 1. The structure has two-dimensional (2D) characteristics built up by rigorously planar (4.6.4.6)-(4.6…”