Stuffed Rare-Earth Garnets.

We report the synthesis and magnetic characterization of stuffed rare-earth gallium garnets, RE 3+ x Ga 5- x O 12 (RE = Lu, Yb, Er, Dy, Gd), for x up to 0.5. The excess rare-earth ions partly fill the octahedral sites normally fully occupied by Ga 3+ , forming disordered pairs of corner-shared face-sharing magnetic tetrahedra. The Curie-Weiss constants and observed effective moments per rare-earth are smaller than are seen for the unstuffed gallium garnets. No significant change in the field-dependent magnetization is observed but missing entropy is seen when integrating the heat capacity down to 0.5 K.