The study focuses on the polarization dynamics of the ferroelectric phase under an external magnetic field in a trilayered magnetoelectric (ME) composite of 0.94(Na_0.5Bi_0.5TiO₃)-0.06BaTiO₃ (NBT-BT)/CoFe₂O₄(CFO)/NBT-BT. With the estimation of gradient size of the strain across the interface, the thin films with varying top layer (NBT-BT) thicknesses were fabricated. The piezoelectric displacement curves revealed the linear characteristics for the 30 nm NBT-BT ME composite due to the presence of dominant interfacial strain. Time-resolved polarization switching studies confirmed the role of interfacial strain on the time scale of polarization switching of the ferroelectric phase. Magnetic field-assisted piezoresponse force microscopy studies confirmed the presence of nonlinear contribution like polarization rotation in the 100 nm NBT-BT ME composite. The interfacial strain was found to operate in a way that imposes constraints on the polarization rotation in a spatial region of ∼20–30 nm away from the interface. However, at a spatial region >30 nm, the interfacial strain was found to supplement the field-induced strain and assisted the polarization rotation to happen. The spatial-dependent behavioral analysis of the interface strain on the polarization dynamics will help in using the ME composite for targeted device applications such as actuators or energy harvesters.

中文翻译：

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用于能量收集的应变工程 0.94(Na0.5Bi0.5TiO3)-0.06BaTiO3/CoFe2O4 磁电纳米复合材料中磁场诱导的极化旋转

_{研究重点是0.94(Na 0.5} Bi _0.5 TiO ₃ )-0.06BaTiO ₃ (NBT-BT)/CoFe ₂ O ₄ (CFO)三层磁电(ME)复合材料中铁电相在外部磁场下的极化动力学。)/NBT-BT。通过估计界面上应变的梯度大小，制造了具有不同顶层（NBT-BT）厚度的薄膜。由于存在主要界面应变，压电位移曲线揭示了 30 nm NBT-BT ME 复合材料的线性特征。时间分辨极化切换研究证实了界面应变对铁电相极化切换时间尺度的作用。磁场辅助压响应力显微镜研究证实了 100 nm NBT-BT ME 复合材料中存在非线性贡献，例如偏振旋转。研究发现，界面应变的作用方式对距界面约 20-30 nm 的空间区域内的偏振旋转施加了限制。然而，在>30 nm的空间区域，发现界面应变补充了场引起的应变并有助于偏振旋转的发生。极化动力学上的界面应变的空间相关行为分析将有助于将 ME 复合材料用于目标设备应用，例如执行器或能量采集器。