Flexoelectricity is a universal property associated with dielectric materials, wherein they exhibit remanent polarization induced by strain gradient. Rare-earth iron garnets, R₃Fe₅O₁₂, are ferrimagnetic insulators with useful magnetic properties. However, they are unlikely to show remanent dielectric polarization because of their centrosymmetric structure. Here, to induce flexoelectricity, we investigate various rare-earth iron-garnet thin films deposited on lattice-mismatched substrates. Atomic-resolution scanning transmission electron microscopy demonstrates the presence of 15 nm-thick strain gradients in Sm₃Fe₅O₁₂ films between epitaxially strained tetragonal and relaxed cubic structures. Furthermore, negatively polarized nanodomains are imaged by scanning nonlinear dielectric microscopy. It suggests a generation of flexoelectricity, where the polarization points down toward the substrate in the out-of-plane direction. X-ray magnetic circular dichroism demonstrates hysteresis with a large coercive field originating from the strain-gradient layer. We believe that our study will pave the way for achieving dielectric polarization even in nonpolar centrosymmetric materials by strain-gradient engineering.

柔性电是与介电材料相关的普遍特性，其中它们表现出由应变梯度引起的剩余极化。稀土铁石榴石R ₃ Fe ₅ O ₁₂是具有有用磁性的亚铁磁绝缘体。然而，由于它们的中心对称结构，它们不太可能表现出剩余的介电极化。在这里，为了诱导挠曲电，我们研究了沉积在晶格失配基板上的各种稀土铁石榴石薄膜。原子分辨率扫描透射电子显微镜证明 Sm ₃ Fe ₅ O _{12 中}存在 15 nm 厚的应变梯度外延应变四方结构和松弛立方结构之间的薄膜。此外，负极化纳米域通过扫描非线性介电显微镜成像。它表明产生了挠曲电性，其中极化在面外方向向下指向基板。X 射线磁性圆二色性显示具有源自应变梯度层的大矫顽场的磁滞现象。我们相信，我们的研究将为通过应变梯度工程在非极性中心对称材料中实现介电极化铺平道路。