Synthesis and Magnetic Properties of the Boride Series MRh6-nRunB3 (M = Co, Ni; N=1-5)

Tuning of the magnetic properties of intermetallic materials is increasingly gaining interest in the chemistry community. We report on the successful synthesis and magnetic characterizations of the two new quaternary boride series MRh6-nRunB3 (M = Co, Ni; 1 <= n <= 5). Powder samples have been synthesized by arc-melting the elements under purified argon in a water-cooled copper crucible. The products were characterized by powder X-ray diffraction through Rietveld refinements as well as EDX measurements. All phases crystallize in the hexagonal Th7Fe3 structure type (space group P6(3)mc, no. 186, Z = 2). In the Co-based series, the lattice parameters decrease linearly with increasing ruthenium content, whereas in the Ni-based series they remain nearly constant for the Rh-rich side then decrease with increasing Ru content. Significant ferromagnetic interactions are observed for the Co-based series, and they decrease linearly with increasing Ru content with magnetic moments decreasing from 0.74 mu(B) (CoRh5RuB3) to 0.13 mu(B) (CoRhRu5B3) at 5 K and 5 T. Pauli paramagnetism dominates the Ni-based series.