Hybrid improper ferroelectrics (HIFs) have been intensely studied over the last few years to gain understanding of their temperature induced phase transitions and ferroelectric switching pathways. Here we report a switching from first- to second-order phase transition pathway for topical HIFs Ca3−xSrxTi2O7, which is driven by the differing entropies of the phases that we identify as being associated with the dynamic motion of octahedral tilts and rotations. A greater understanding of the transition pathways in this class of layered perovskites, which host many physical properties that are coupled to specific symmetries and octahedral rotation and tilt distortions -- such as superconductivity, negative thermal expansion, fast ion conductivity, ferroelectricity, among others -- is a crucial step in creating novel functional materials by design.
@article{arxiv.2001.05189,
title = {From first- to second-order phase transitions in hybrid improper ferroelectrics through entropy stabilisation},
author = {Fernando Pomiro and Chris Ablitt and Nicholas C. Bristowe and Arash A. Mostofi and Coongjae Won and Sang-Wook Cheong and Mark S. Senn},
journal= {arXiv preprint arXiv:2001.05189},
year = {2020}
}