Crystal growth, characterization, and phase transition of PbCuTe2O6

Single crystals of the three-dimensional frustrated magnet and spin liquid candidate PbCuTe2O6 were grown using both the traveling solvent floating zone and the top-seeded solution growth (TSSG) techniques. The growth conditions were optimized by investigating the thermal properties. The quality of the crystals was checked by polarized optical microscopy, x-ray Laue, and x-ray powder diffraction and compared to the polycrystalline samples. Excellent quality crystals were obtained by the TSSG method. Magnetic measurements of these crystals revealed a small anisotropy for different crystallographic directions in comparison with the previously reported data. The heat capacity of both single-crystal and powder samples reveal a transition anomaly around 1 K. Curiously the position and magnitude of the transition are strongly dependent on the crystallite size, and it is almost absent for the smallest crystallites. A structural transition is suggested which accompanies the reported ferroelectric transition, and a scenario whereby it becomes energetically unfavorable in small crystallites is proposed.