Pyrochlore-related compounds of the $R_2{\text{FeTaO}}_7$ type (with $R=\text{Gd}$, Eu, Dy, and Y) were synthesized by solid-state reaction of precursor oxides. The compounds were structurally and magnetically characterized by x-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. The results revealed that this subfamily of pyrochlores crystallizes with the $\mathbf{R}\overline{\mathbf{3}}$ symmetry, where iron with tantalum occupies two different crystallographic sites. Magnetic phase transition to a long-range ordered state was not observed down to 2 K, although islands of magnetically oriented iron atoms could be detected.

• Received 26 June 2009

DOI:https://doi.org/10.1103/PhysRevB.81.014417