Rare‐Earth Cobalt Gallides RE4Co3Ga16 (RE = Gd–Er, Y): Self‐Interstitial Derivatives of RE2CoGa8

Ternary rare-earth cobalt gallides RE4Co3Ga16 (RE = Gd-Er, Y) have been prepared by arc-melting of the elements followed by annealing at 800 degrees C. Single crystals of the Gd and Tb members were also grown in the presence of a Ga self-flux. They extend the rare-earth substitution possible in the Sm4Co3Ga16-type structure (Pearson symbol tP23, space group P4/mmm, Z = 1), in which additional Co atoms enter as self-interstitials into the parent RE2CoGa8 structure. Structural refinements were carried out on single-crystal (RE = Gd, Tb) and powder (RE = Dy, Ho, Er, Y) X-ray diffraction data. Cell parameters lie in the ranges of a = 6.03-5.96 angstrom and c = 11.11-10.96 angstrom. Magnetic measurements on RE4Co3Ga16 (RE = Gd, Tb, Dy) reveal that they order antiferromagnetically below T-N of 19, 25, and 14 K, respectively; Y4Co3Ga16 is Pauli paramagnetic. The electrical resistivity of Tb4Co3Ga16 undergoes a transition coincident with the magnetic ordering temperature. Band structure calculations on Y4Co3Ga16 indicate that the major bonding contributions arise from Co-Ga and Ga-Ga interactions, with the stuffing of interstitial Co atoms into octahedral sites of the parent Y2CoGa8 structure, which provides additional Co-Ga bonding stabilization.