Ternary intermetallic compounds R23Ru7In4 (R=Ce, Pr): Synthesis, crystal structure and physical properties

Two novel ternary intermetallic compounds Ce23Ru7In4 and Pr23Ru7In4 were synthesized by arc melting of components and subsequent annealing at 600 degrees C. Both compounds crystallize in a hexagonal cell, with structure type Pr23Ir7Mg4, space group P6(3)mc (& numero; 186), Pearson symbol hP68, Z = 2, the cell parameters: a = 9.861(5) & Aring;, c = 22.520(12) & Aring; (Ce); a = 9.9260(7) & Aring;, c = 22.4109(2) & Aring; (Pr). The structure of Ce23Ru7In4 was determined by single-crystal X-ray diffraction and the structure of Pr23Ru7In4 was determined by the Rietveld method using powder X-ray diffraction pattern. Compound Ce23Ru7+xIn4-x exist in the homogeneity range 0 <= x <= 3. An essential feature of compound Ce23Ru7In4 is the presence of abnormally short distances Ce-Ru (2.637 & Aring;, 2.735 & Aring;). The compound Pr23Ru7In4 melts incongruently and compound Ce23Ru7In4 melts congruently at temperatures 756 and 683 degrees & Scy; respectively. The Pr23Ru7In4 compound is characterized by the presence of a magnetic transition at 12 K. The observed magnetic transition is most likely indicative of a transition to the spin glass state.