The results of a single-crystal X-ray-diffraction study of the evolution of crystal structures of VI3 with temperature with emphasis on phase transitions are presented. Some related specific-heat and magnetization data are included. The existence of the room-temperature trigonal crystal structure R-3 (148) has been confirmed. Upon cooling, VI3 undergoes a structural phase transition to a monoclinic phase at Ts ~ 79 K. Ts is reduced in magnetic fields applied along the trigonal c-axis. When VI3 becomes ferromagnetic at TFM1 ~ 50 K, magnetostriction-induced changes of the monoclinic-structure parameters are observed. Upon further cooling, the monoclinic structure transforms into a triclinic variant at 32 K which is most likely occurring in conjunction with the previously reported transformation of the ferromagnetic structure. The observed phenomena are preliminarily attributed to strong magnetoelastic interactions.
@article{arxiv.1909.04459,
title = {Crystal Structures and Phase Transitions of the van-der-Waals Ferromagnet VI3},
author = {Petr Doležal and Marie Kratochvílová and Václav Holý and Petr Čermák and Vladimír Sechovský and Michal Dušek and Martin Míšek and Tirthankar Chakraborty and Yukio Noda and Suhan Son and Je-Geun Park},
journal= {arXiv preprint arXiv:1909.04459},
year = {2019}
}