Making EuO multiferroic by epitaxial strain engineering
Making EuO multiferroic by epitaxial strain engineering
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DOI：
10.1038/s43246-020-00075-1
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发表时间：
2020-10-14
影响因子：
7.8
通讯作者：
Kamba, Stanislav
中科院分区：
文献类型：
--
作者：
Goian, Veronica;Held, Rainer;Kamba, Stanislav
多铁性材料是同时具有铁电性和理想铁磁性的材料。不幸的是，大多数已知的磁电多铁性结合了铁电性与反铁磁性或弱铁磁性。在此，根据先前的理论预测，我们提供了明确的实验证据，表明铁磁性简单二元氧化物EuO中的外延拉伸应变可以诱导铁电性。我们利用红外反射光谱研究了铁电相变，发现软光学声子的频率随着拉伸应变的增加和温度的降低而降低。我们在（LaAlO3）(0.29)-(SrAl1/2Ta1/2O3)（0.71）衬底上外延生长的（EuO）(2)/(BaO)(2)超晶格在100K下观察到这种软模式异常，这是位移铁电相变的典型特征。该超晶格中的EuO名义上承受6.4%的双轴拉伸应变，即比先前发表的计算所需的拉伸应变多50%。我们使用混合泛函解释了新的第一性原理密度泛函计算结果，与以前使用的局部密度近似和广义梯度近似泛函相比，它提供了与实验更好的定量一致性。
Multiferroics are materials exhibiting the coexistence of ferroelectricity and ideally ferromagnetism. Unfortunately, most known magnetoelectric multiferroics combine ferroelectricity with antiferromagnetism or with weak ferromagnetism. Here, following previous theoretical predictions, we provide clear experimental indications that ferroelectricity can be induced by epitaxial tensile strain in the ferromagnetic simple binary oxide EuO. We investigate the ferroelectric phase transition using infrared reflectance spectroscopy, finding that the frequency of the soft optical phonon reduces with increasing tensile strain and decreasing temperature. We observe such a soft mode anomaly at 100K in (EuO)(2)/(BaO)(2) superlattices grown epitaxially on (LaAlO3)(0.29)-(SrAl1/2Ta1/2O3)(0.71) substrates, which is a typical signature for a displacive ferroelectric phase transition. The EuO in this superlattice is nominally subjected to 6.4% biaxial tensile strain, i.e., 50% more than believed needed from previously published calculations. We interpret our results with new first-principles density functional calculations using a hybrid functional, which provides a better quantitative agreement with experiment than the previously used local-density approximation and generalized gradient approximation functionals.