Swamynadhan M J, Ghosh Ayana, Ghosh Saurabh
Department of Physics and Nanotechnology, Faculty of Engineering and Technology, SRM Institute of Science and Technology, Kattankulathur-603 203, Tamil Nadu, India.
Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, 37831, TN, USA.
Mater Horiz. 2023 Nov 27;10(12):5942-5949. doi: 10.1039/d3mh01285a.
Hybrid improper ferroelectricity is a useful tool to design ABO/A'BO polar superlattices from non polar building blocks. In this study, we have designed high polarization-low switching barrier hybrid improper ferroelectric superlattices with efficient polarization, and polarization-magnetization switching properties above room temperature, using density functional theory and molecular dynamics simulations. Superlattices with a chemical formula of (AAlO)/(A'AlO), where / = 1/1, 1/3, 3/1, 1/5 and 5/1, A, A' = Lanthanide and Y cations are considered to outline the design principles behind polarization switching and (LaFeO)/(CeFeO) is investigated for polarization-magnetization switching. We find that the unconventional switching paths out-of-phase rotation () and tilt precession always yield lower switching barrier compared to those in-phase rotation () and tilt () of BO octahedra. Results from molecular dynamics simulations estimate the temperature at which the lowest energy barrier can be overcome. It is possible to tune the polarization switching barrier by tuning the tolerance factor, A,A' cation radius mismatch and super lattice periodicity. For switching , the switching barrier varies exponentially with rotation angle, indicating how high switching barrier is expected for systems, away from cubic symmetry. We provide a recipe to overcome such a bottleneck by tuning superlattice periodicity. Finally, we have proposed the multiferroic device application concept through a proposed polarization-temperature hysteresis loop and magnetization switching.
混合非本征铁电性是一种利用非极性结构单元设计ABO/A'BO极性超晶格的有效工具。在本研究中，我们利用密度泛函理论和分子动力学模拟，设计了具有高效极化以及高于室温的极化-磁化切换特性的高极化-低切换势垒混合非本征铁电超晶格。考虑了化学式为(AAlO)/(A'AlO)（其中/ = 1/1、1/3、3/1、1/5和5/1，A、A' = 镧系元素和Y阳离子）的超晶格，以概述极化切换背后的设计原理，并研究了(LaFeO)/(CeFeO)的极化-磁化切换。我们发现，与BO八面体的同相旋转（）和倾斜（）相比，非传统的切换路径——异相旋转（）和倾斜进动——总是产生更低的切换势垒。分子动力学模拟结果估计了能够克服最低能量势垒的温度。通过调整容差因子、A、A'阳离子半径失配和超晶格周期性，可以调节极化切换势垒。对于切换，切换势垒随旋转角度呈指数变化，这表明对于远离立方对称性的系统，预期的切换势垒有多高。我们提供了一种通过调整超晶格周期性来克服这一瓶颈的方法。最后，我们通过提出的极化-温度滞后回线和磁化切换，提出了多铁性器件应用概念。
