Flexoelectric nanodomains in rare-earth iron garnet thin films under strain gradient-猫眼课题宝

DOI：

10.1038/s43246-021-00199-y

发表时间：

2021-09

期刊：

Communications Materials

影响因子：

7.8

通讯作者：

中科院分区：

文献类型：

作者：

H. Yamahara;B. Feng;M. Seki;Masaki Adachi;Md Shamim Sarker;T. Takeda;Masaki Kobayashi;R. Ishikawa;Y. Ikuhara;Yasuo Cho;H. Tabata

挠性电是与介质材料相关的一种普遍性质，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，R3Fe5O12，是一种具有有用的磁性的亚铁磁性绝缘体。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，我们研究了在晶格失配的衬底上沉积的各种稀土铁榴石薄膜。原子分辨扫描电子显微镜显示，Sm3Fe5O12薄膜在外延应变的四方结构和弛豫立方结构之间存在15 nm厚的应变梯度。此外，还利用扫描非线性介电显微镜对负极化纳米微区进行了成像。它暗示了一种挠性电的产生，其中极化在平面外方向指向基片。X射线磁圆二向色性显示了磁滞回线，应变梯度层产生了较大的矫顽场。我们相信，我们的研究将为通过应变梯度工程实现非极性中心对称材料的介电极化铺平道路。

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 Sm3Fe5O12films 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.

Flexoelectric nanodomains in rare-earth iron garnet thin films under strain gradient

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