Symmetry and three-dimensional anisotropy of polar domain boundaries observed in ferroelastic LaAlO3 in the complete absence of ferroelectric instability
Symmetry and three-dimensional anisotropy of polar domain boundaries observed in ferroelastic LaAlO3 in the complete absence of ferroelectric instability
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DOI：
10.1103/physrevb.98.104105
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发表时间：
2018-09
影响因子：
3.7
通讯作者：
H. Yokota;S. Matsumoto;E. Salje;Y. Uesu
中科院分区：
文献类型：
--
作者：
H. Yokota;S. Matsumoto;E. Salje;Y. Uesu
利用非线性光学二次谐波显微镜研究了铁弹（LAO）材料的畴界。虽然散装结晶LAO具有中心对称性，本质上是非SH活性，我们的三维观察表明，LAO的域边界表现出SH活动几乎相同的幅度内的边界。SH强度的偏振依赖性表现出很强的各向异性，这可以用极性三角点群来解释。发现极向是沿着轴向并从畴界面倾斜。这意味着，双阶参数的双二次耦合方案可能是域边界出现极性的主要原因。我们的实验结果与文献[1]的结果一起表明，铁弹材料中畴界的极性性质可能是一种普遍存在的现象。
The domain boundaries of ferroelastic(LAO) are examined using a nonlinear optical second harmonic generation (SHG) microscope. Although bulk crystalline LAO possesses centro-symmetry and is inherently non-SH active, our three-dimensional observations reveal that the domain boundaries of LAO exhibit SH activity with almost the same magnitude within a boundary. The polarization dependence of the SH intensities shows strong anisotropy, which is explained by the polar trigonal point group,. The polar direction is found to be along theaxis and inclined from the domain boundary plane. It implies that the biquadratic coupling scheme of two order parameters could be the main origin of the emergence of polar nature at the domain boundary. Our experimental results together with those ofsuggest that the polar nature of the domain boundary in ferroelastic materials may be a ubiquitous phenomenon.