Crystal growth, characterization and phase transition of PbCuTe$_2$O$_6$

TL;DR

This study reports the successful growth and detailed characterization of high-quality PbCuTe$_2$O$_6$ single crystals, revealing a size-dependent phase transition and potential structural-ferroelectric coupling in this frustrated magnet candidate.

Contribution

It introduces optimized crystal growth methods for PbCuTe$_2$O$_6$ and uncovers size-dependent phase transition phenomena not previously reported.

Findings

High-quality single crystals were grown using TSSG method.

A phase transition around 1 K was observed, dependent on crystallite size.

Structural transition may be linked to ferroelectric behavior.

Abstract

Single crystals of the three-dimensional frustrated magnet and spin liquid candidate compound PbCuTe$_2$O$_6$ were grown using both the Travelling Solvent Floating Zone (TSFZ) 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 entirely absent for the smallest crystallites. A structural transition is suggested which accompanies the reported ferroelectric transition, and a scenario whereby it becomes energetically unfavourable in small crystallites is proposed.