Scandium iridium boride Sc3Ir5B2 and the quaternary derivatives Sc2MIr5B2 with M = Be, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, or Ge: Preparation, crystal structure, and physical properties

The new compounds Sc3Ir5B2 and Sc2MIr5B2 with M = Be, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, or Ge were prepared by arc-melting appropriate compressed mixtures of the elemental components in an argon atmosphere. They crystallize tetragonally with Z = 2 in the space group P4/mbm. According to powder diagrams, all compounds are isotypic. Structure determinations based on single-crystal X-ray data were performed for Sc2SiIr5B2, Sc2VIr5B2, and Sc2FeIr5B2. Sc3Ir5B2 crystallizes with the Ti3Co5B2-type compounds, while the quaternary compounds form an ordered substitutional variant of this structure. The M atoms are arranged in rows along [001] with M-M distances of ∼300 pm in the rows and ∼660 pm between the rows. For the compounds with M = Mn, Fe, or Co, this results in highly anisotropic magnetic properties. Susceptibility measurements with a Faraday balance in the range 7--770 K suggest ferromagnetic coupling in the rows at low temperatures. Between the rows, the coupling was antiferromagnetic for Sc2FeIr5B2 (TN ∼ 190 K) and ferromagnetic for Sc2MnIr5B2 (TC ∼ 115 K, μs ∼ 1.2 μB) and for Sc2CoIr5B2 (TC ∼ 135 K, μs ∼ 1.2 μB). The temperature dependence of the resistivity was measured for the compounds with M = Si, Mn, Fe, and Co