Crystal structure and magnetic properties of a new oxyselenide of gadolinium and titanium:: Gd4TiSe4O4

A new compound Gd4TiSe4O4 has been obtained by a solid state reaction of Gd2O3, TiO2, and TiSe2, at T = 1000degreesC, with the addition of iodine to favor crystallization. Single-crystal X-ray diffraction measurements show that Gd4TiSe4O4 crystallizes in space group C2/m (No. 12) of the monoclinic system with two formula units in a cell of dimensions a = 15.7878(4) Angstrom, b = 3.7610(2) Angstrom, c = 9.6639(3) Angstrom, and beta = 117.569(2)degrees. The structure contains two crystallographically independent Gd atoms with a bicapped trigonal prismatic coordination. Association of four adjacent Gd-centered polyhedra constitutes the elemental building unit, which develops into ribbons along b. The ribbons are interconnected by infinite chains of edge-sharing Ti-centered octahedra. Magnetic susceptibility of the title compound has been measured from 1.8 to 300 K, and from B = 1.10(-3) to 0.1T for the ZFC and FC cooling modes. The linear variation of the inverse susceptibility versus T can be modeled with a Curie-Weiss law in agreement with a Gd3+ free ion behavior. The maximum of the chi(T) curve at about 2.5 K could be attributed to both an antiferromagnetic transition and the saturation of the weak ferromagnetic component. (C) 2001 Elsevier Science.