  Several x-compositions of the polycrystalline Dy3-xYxTaO7 system,
crystallizing in the weberite-type structure, were synthesized and structurally
characterized using Rietveld refinements based on X-ray diffraction data. In
previous magnetic characterization of Dy3TaO7 (x = 0), with the same crystal
structure, an antiferromagnetic transition at T = 2.3 K has been assigned to
this compound. On the basis of DC and AC magnetic susceptibilities analyses, we
show in this work that all compounds in the x range of 0-1.0 exhibit a spin
glass behavior. The nature of the spin glass behavior in Dy3-xYxTaO7, can be
attributed to the highly frustrated antiferromagnetic interaction of the Dy3+
sublattice and to the Dy3+-Dy3+ distorted tetrahedra array in the weberite-type
structure of this system. By fitting AC susceptibility data, using dynamical
scaling theory equations, we conclude that a cluster spin glass is present in
Dy3-xYxTaO7 in the low temperature range. Depending on the x-composition, Tg ~
2.2 - 3.2 K. In the range 15-300 K the system obeys a Curie-Weiss magnetic
behavior.
