npj: 外延BaTiO3—一种新型电子工程材料

海归学者发起的公益学术平台

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单相材料中铁电性、导电性和磁性的共存具有巨大的技术和应用潜力，引起了人们的广泛关注。然而，它们相互排斥的机制妨碍了多功能导电多铁材料的发现。

来自上海材料基因组研究所的徐涛博士和日本京都大学的Takahiro Shimada博士共同领导的团队，提出了一种新的材料设计方法，以通过电子能带工程使这些相互矛盾的材料性质可以共存。他们使用第一原理计算证明了适当的机械应变可以通过调节电子-声子耦合，将掺杂BaTiO₃中过量电子从自由载流子构型转变为局域极化态。所得到的局域自旋极化电子在主铁电性作用下仍然存在，因而表现为多铁极化子。这些多铁性质进一步与电子导电性共存，该现象源于电子极化子的强迁移率。因此，通过机械调控有意地改变电子结构，可能成为一种有希望实现不寻常的共存特性和新技术突破的范例。

该文近期发表于npj Computational Materials 5: 23 (2019)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Electron engineering of metallic multiferroic polarons in epitaxial BaTiO₃

Tao Xu, Takahiro Shimada, Yasumitsu Araki, Masataka Mori, Gen Fujimoto, Jie Wang, Tong-Yi Zhang & Takayuki Kitamura 

The coexistence of ferroelectricity, conductivity, and magnetism in a single-phase material has attracted considerable attention due to fundamental interest and tremendous technological potential. However, their mutually exclusive mechanisms hinder the discovery of multifunctional conducting multiferroics. Here, we propose a new material design approach for electron engineering to enable these conflicting properties to coexist. We use first principles calculations to demonstrate that appropriate mechanical strain can turn the excess electrons in doped BaTiO₃from a free-carrier configuration to a localized polaronic state by modulating the electron–phonon coupling. The resulting localized spin-polarized electron survives the host ferroelectricity and consequently manifests as a multiferroic polaron. The multiferroic properties coexist with the electronic conductivity arising from the high-hopping mobility of the polaron, which enables the doped epitaxial BaTiO3 to act as a multiferroic conducting material. This mechanical control over the electron configuration is a potential path toward unusual coexisting properties.

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