Synthesis, Crystal Chemistry and Magnetism of the Metal-rich Borides

Powder samples and single crystals of the boride phases MxRh7−xB3 (M = Cr, Mn, Ni; x≤ 1) have been synthesized from the elements using an arc-melting furnace under purified argon atmosphere in a water-cooled copper crucible. The new phases were characterized from single-crystal and powder X-ray diffraction, as well as semi-quantitative EDX measurements. The obtained phases crystallize in the hexagonal Th7Fe3 structure type (space group P63mc, no. 186, Z = 2). In all cases (M = Cr, Mn, Ni), M is found to preferentially mix with rhodium at only one (6c) of the three available rhodium positions. Pauli paramagnetism was observed in CrxRh7−xB3 (x < 1), whereas both Pauli and temperature-dependent paramagnetisms were found in NiRh6B3.