The structure and magnetic properties of the ternary intermetallic compounds La2Co17-xTax

Novel ternary intermetallic compounds La2Co17-xTax (x = 0.5 and 0.6) with the Th2Zn17-type structure were synthesized with Ta as a stabilizing element, and their crystal structures and magnetic properties were investigated by x-ray powder diffraction and magnetic measurement. The lattice parameters are a = 8.5092, c = 12.3575 Angstrom for x = 0.5, and a = 8.5104, c = 12.3591 Angstrom for x = 0.6. Rietveld refinement of the crystal structure reveals that Ta atoms occupy exclusively 6c crystallographic positions. The preferential occupation of Ta atoms can be understood in terms of the site volume and enthalpy of mixing. These compounds exhibit favourable uniaxial magnetocrystalline anisotropy parallel to c-axis. The Curie temperature T-C and saturation moment MS are 1032 K and 104.3 A m(2) kg(-1) for x = 0.5, and 1020 K and 98.5 A m(2) kg(-1) for x = 0.6, respectively.