Strain-mediated elastic coupling in magnetoelectric nickel/barium-titanate heterostructures
Strain-mediated elastic coupling in magnetoelectric nickel/barium-titanate heterostructures
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DOI：
10.1103/physrevb.87.054410
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发表时间：
2013-02
影响因子：
3.7
通讯作者：
R. Streubel;D. Köhler;R. Schäfer;L. Eng
中科院分区：
文献类型：
--
作者：
R. Streubel;D. Köhler;R. Schäfer;L. Eng
多铁性纳米材料具有组装多种新颖和智能设备的潜力。然而，对于室温（RT）应用，迄今为止只有BiFeO单相钙钛矿是潜在的候选者。然而，现在广泛提出将磁性和铁电功能性分离到不同层中的垂直异质结构以规避材料可用性的这种缺乏。我们在这里表明，第二种方法是非常有益的，如这两个层之间的应变介导的耦合所示，即，铁电钛酸钡单晶（BTO）和磁致伸缩镍（Ni）薄膜。通过在BTO衬底上施加电场，Ni薄膜的易磁化轴旋转90 °，从而产生tokJ/m范围内的磁各向异性。我们表明，本地开关收益通过成核和直的内尔畴壁的生长在曲折的墙壁成本。该过程是完全可逆的，连续可调的磁光克尔显微镜和磁力显微镜探测局部面内和面外磁化，分别与调查。此外，各向异性的程度可以通过在室温、高于BTO的居里温度或在中间温度下沉积Ni膜来预先设计。我们的研究结果提供了证据，在现代设备中使用报告的耦合，如磁阻随机存取存储器，自旋阀，自旋极化电子发射，但同样为自下而上组装的磁化分子纳米结构，通过磁畴壁工程。
Multiferroic nanomaterials bear the potential for assembling a manifold of novel and smart devices. For room temperature (RT) applications, however, only the BiFeOsingle-phase perovskites are potential candidates to date. Nevertheless, vertical heterostructures separating magnetic and ferroelectric functionality into different layers are now widely proposed to circumvent this lack in materials’ availability. We show here that the second approach is very profitable as illustrated by the strain-mediated coupling between such two layers, i.e., a ferroelectric barium titanate single-crystal (BTO) and a magnetostrictive nickel (Ni) thin film. Applying an electric field across the BTO substrate forces the magnetic easy axis in the Ni film to rotate by 90, resulting in a magnetic anisotropy in the range oftokJ/m. We show that local switching proceeds through the nucleation and growth of straight Néel-domain walls at a cost of zigzag walls. The process is fully reversible and continuously tunable as investigated with magnetooptical Kerr microscopy and magnetic force microscopy probing the local in-plane and out-of-plane magnetizations, respectively. Moreover, the degree of anisotropy can be pre-engineered by depositing the Ni film either at RT, above the Curie temperatureof BTO, or at an intermediate temperature. Our findings give evidence for using the reported coupling in modern devices, such as magnetoresistive random access memories, spin valves, spin-polarized electron emission, but equally for the bottom-up assembling of magnetizable molecular nanostructures through magnetic domain wall engineering.