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arXiv · 2503.11033

A-site Cation disorder engineering in Ruddlesden-Popper Layered Perovskite Oxide La2(Ba,Sr)In2O7 for Ferroelectricity

Takumi Terauchi·Wei Yi·Rikuto Takada Hirofumi Akamatsu Ryo Ota Shuki Torii·Koji Fujita
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Abstract

The strategic design of ferroelectric materials exhibiting robust and reversible spontaneous polarization remains a pivotal challenge in functional materials research. Here, A-site cation disorder engineering is employed in the n = 2 Ruddlesden-Popper layered perovskite La2Ba1-xSrxIn2O7 to achieve room-temperature ferroelectricity. Systematic substitution of Sr2+ for Ba2+ drives symmetry transitions from a parent centrosymmetric (CS) P42/mnm structure (x = 0) to two emergent phases: a CS Amam phase (for x from 0.3 to 0.4) and a polar A21am phase (for x from 0.5 to 0.9). Multimodal characterization combining synchrotron diffraction, neutron scattering, nonlinear optical spectroscopy, and hysteresis loop of electric polarization versus electric field reveals a hybrid improper ferroelectric (HIF) mechanism in the A21am phase, arising from trilinear coupling between octahedral rotations and tilts. Cation disorder at A-sites suppresses the interfacial rumpling-induced octahedral elongation (deformation) while enhancing the octahedral rotations which are critical for the polar symmetry stabilization. First-principles calculations further elucidate that Sr/La disorder mitigates electrostatic interactions, enabling oxygen octahedral distortions necessary for ferroelectricity. This work establishes cation disorder engineering as a versatile strategy to design high-temperature multiferroics in layered perovskites, advancing the coupling between structural distortions and functional responses in complex oxides.

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Takumi Terauchi, Wei Yi, Rikuto Takada Hirofumi Akamatsu Ryo Ota Shuki Torii, Koji Fujita. 2025-03-14. A-site Cation disorder engineering in Ruddlesden-Popper Layered Perovskite Oxide La2(Ba,Sr)In2O7 for Ferroelectricity. https://arxiv.org/abs/2503.11033

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