Abstract
Through arc-melting reactions of the elements and annealing at 800 °C, the ternary rare-earth germanides RE3Ru2Ge3 and RE3Ir2Ge3 have been prepared for most of the smaller RE components (RE=Y, Gd–Tm, Lu). In the iridium-containing reactions, the new phases RE2IrGe2 were also generally formed as by-products. Powder X-ray diffraction revealed orthorhombic Hf3Ni2Si3-type structures (space group Cmcm, Z=4) for RE3M2Ge3 (M=Ru, Ir) and monoclinic Sc2CoSi2-type structures (space group C2/m, Z=4) for RE2IrGe2. Full crystal structures were determined by single-crystal X-ray diffraction for all members of RE3Ru2Ge3 (a=4.2477(6) Å, b=10.7672(16) Å, c=13.894(2) Å for RE=Y; a=4.2610(3)–4.2045(8) Å, b=10.9103(8)–10.561(2) Å, c=14.0263(10)–13.639(3) Å in the progression of RE from Gd to Lu) and for Tb3Ir2Ge3 (a=4.2937(3) Å, b=10.4868(7) Å, c=14.2373(10) Å). Both structures can be described in terms of CrB- and ThCr2Si2-type slabs built from Ge-centred trigonal prisms. However, band structure calculations on Y3Ru2Ge3 support an alternative description for RE3M2Ge3 based on [M2Ge3] layers built from linked MGe4 tetrahedra, which emphasizes the strong M–Ge covalent bonds present. The temperature dependence of the electrical resistivity of RE3Ru2Ge3 generally indicates metallic behaviour but with low-temperature transitions visible for some members (RE=Gd, Tb, Dy) that are probably associated with magnetic ordering of the RE atoms. Anomalously, Y3Ru2Ge3 exhibits semiconductor-like behaviour of uncertain origin. Magnetic measurements on Dy3Ru2Ge3 reveal antiferromagnetic ordering at 3 K and several unusual field-dependent transitions suggestive of complex spin reorientation processes.
Published Version
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