arXiv subjects

Alexander Lione

Publications and source records attributed to Alexander Lione.

2 recordsLinked to original sources

arXiv2026

Alternative origins of polarity in compressively strained SrTiO3-RENiO3 capacitors

Since its original prediction 25 years ago, room-temperature out-of-plane ferroelectricity in compressively strained SrTiO3 remains an ongoing pursuit. In this work, we investigate the structural, electrical and electromechanical properties of highly strained epitaxial SrTiO3 capacitors with rare earth nickelate electrodes. The SrTiO3 layers experience compressive strains up to -3% and exhibit pronounced tetragonality, comparable to that of bulk PbTiO3. Variable-temperature electrical measurements and room-temperature piezoresponse force microscopy reveal butterfly-shaped capacitance-voltage hysteresis and domain-like electromechanical response typical of ferroelectric materials. However, the overall behavior is inconsistent with a stable ferroelectric state. We therefore propose an alternative mechanism for the observed polarity in our samples based on spatially inhomogeneous internal fields. Our first-principles calculations show that such fields may arise from charge discontinuities between the formally charged NdNiO3 layers and charge-neutral SrTiO3 layers.

cond-mat.mtrl-sci↗

arXiv2025

First principles study of [111]-oriented epitaxially strained Rare-Earth Nickelate NdNiO$_3$

Density functional theory is used to investigate the effect of biaxial strain on the structural, electronic and magnetic properties of [111]-oriented NdNiO$_3$, as a representative of the rare-earth perovskites that undergo metal-to-insulator transitions. We find that this constraint on the system induces unique structural phase transitions not previously observed under the well-studied bulk or [001]-oriented strained systems. We also report unique electronic behaviour, including amplification of the electronic band-gap with tensile strain, and insulating, charge-ordered phases with non-orthorhombic tilt patterns. To provide clarity to the trends we observe, we also investigate the coupling between the breathing mode and strain, where we observe certain strains to directly favour and disfavour the creation of the breathing mode (and thus the associated charge-ordering). The amplification of the band gap with strain is understood in terms of a cooperative coupling between the elastic constraint and octahedral breathing, which expands on the previously reported triggered mechanism mediated by octahedral tilting.

cond-mat.mtrl-sci↗