Structure of Gd_0.95Bi_0.05Fe₃(BO₃)₄ single crystals at 293 and 90 K

The structure of GdFe₃(BO₃)₄ single crystals has been studied by X-ray diffraction at 293 and 90 K. The crystals are grown from a flux in the Bi₂Mo₃O₁₂–B₂O₃–Li₂MoO₄–Gd₂O₃–Fe₂O₃ system. The results of chemical analysis and structural study show that these crystals contain bismuth as an impurity. It is found that bismuth atoms are located at gadolinium sites in the structure. A decrease in the temperature is accompanied by a lowering of the symmetry from sp. gr. R32 (at 293 K) to sp. gr. P3₁21 (at 90 K). The presence of two types of iron chains with different geometries at 90 K promotes a change in the magnetic properties of these crystals with a decrease in the temperature.