Structural and magnetic properties of TlCo2-xCuxSe2, 0 <= x <= 1

Structural and magnetic properties of single-crystal TlCo2-xCuxSe2, 0 less than or equal to x less than or equal to 1, have been investigated by means of X-ray diffraction experiments and magnetisation measurements. TlCo2Se2 and TlCu2Se2 are isostructural, belonging to the ThCr2Si2 structure type, i .e. tetragonal sheet structures. From diffraction data on the solid solutio ns, we note superstructure formation at large Cu concentrations. The overal l ordering at low temperature is antiferromagnetic, and the Neel temperatur es scale linearly with x, falling drastically from 82 K (x = 0) to 11 K (x = 1). From fits to the Curie-Weiss law, the effective magnetic moments mu(e ff) and the asymptotic Curie temperatures theta(p) were obtained. theta(p) is positive, showing that the interactions within the sheets are of a ferro magnetic character. (C) 2000 Elsevier Science B.V. All rights reserved.