LAUSR

Abstract In this work, we present both structural and magnetic (DC magnetization and AC susceptibility) studies of the Dy 3−x Y x TaO 7 solid solution. The structural characterization of samples was performed by Rietveld refinements of the X-ray diffraction data. All compounds crystallized in a weberite-related structure in the orthorhombic C222 1 space group (No. 20); the variations of the lattice parameters obey the Vegard´s law in the whole range of composition. DC magnetic measurements of the Dy 3−x Y x TaO 7 system showed a Curie-Weiss paramagnetic behaviour, with antiferromagnetic interactions at T>150 K. Below 3 K a spin glass behaviour in the 0 ≤ x ≤ 1 range of the solid solution was observed. The stoichiometric Dy 3 TaO 7 compound showed spin glass behaviour although there is no evidence of structural disorder. For some Y 3+ doped compounds (x = 0.33, 0.66 and 1.0), chemical disorder reduced the freezing temperature (T g ) values with a × 1/3 dependence. Cole-Cole analysis of the AC magnetic field response showed similar phenomenological parameters for the stoichiometric (x = 0) and the Y 3+ doped compounds with spin glassiness, suggesting an analogous mechanism for these compounds. For the Dy 3−x Y x TaO 7 system, in which the spin glass behaviour seems to exhibit a critical concentration, a magnetic phase diagram is proposed.