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arXiv · 2001.05189

From first- to second-order phase transitions in hybrid improper ferroelectrics through entropy stabilisation

Fernando Pomiro·Chris Ablitt·Nicholas C. Bristowe·Arash A. Mostofi·Coongjae Won·Sang-Wook Cheong·Mark S. Senn
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Abstract

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 $Ca_{3-x}Sr_xTi_2O_7$, 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.

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Fernando Pomiro, Chris Ablitt, Nicholas C. Bristowe, Arash A. Mostofi, Coongjae Won, Sang-Wook Cheong, Mark S. Senn. 2020-01-15. From first- to second-order phase transitions in hybrid improper ferroelectrics through entropy stabilisation. https://doi.org/10.1103/physrevb.102.014101

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