Diverse interface effects on ferroelectricity and magnetoelectric coupling in asymmetric multiferroic tunnel junctions: the role of the interfacial bonding structure
Diverse interface effects on ferroelectricity and magnetoelectric coupling in asymmetric multiferroic tunnel junctions: the role of the interfacial bonding structure
复制标题
非对称多铁隧道结中铁电和磁电耦合的不同界面效应：界面键合结构的作用
DOI：
10.1039/c5cp05207f
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发表时间：
2016
影响因子：
3.3
通讯作者：
Yue Zheng
中科院分区：
文献类型：
--
作者：
X. T. Liu;W. J. Chen;G. L. Jiang;B. Wang;Yue Zheng
电/磁序和磁电耦合的界面和尺寸效应对于基于多铁隧道结的量子尺寸功能器件的现代应用至关重要。为了全面研究界面和尺寸效应，使用第一原理模拟计算了典型的非对称多铁性隧道结（即 Fe/BaTiO3/Co）的性能。最重要的是，所有八种可能的结构以及四种电极/铁电界面组合（即 Fe/BaO、Fe/TiO2、Co/BaO 和 Co/TiO2）和一系列势垒厚度都已考虑在内。这项工作对平衡构型、极化、电荷密度、自旋密度和磁矩等进行了完整的模拟和全面的分析。研究发现，铁电稳定性是由短程化学键和长程去极化/内置场的强度竞争的结果决定的。 M/BaO（M = 磁性金属）端子表现出界面附近局部极化的显着增强，并增加了铁电体的临界厚度。 M/TiO2 界面处良好地保持了偏振的双稳定性。同时，界面处原子上的感应磁矩相当局部化，并受局部界面构型支配。反转电极化可以改变感应磁矩，其中 M-O-Ti 和 M-Ti-O 链中的原子优先被磁化。此外，界面磁矩之和的差异也随着势垒厚度的增加而增大。我们的研究为非对称多铁隧道结中界面、尺寸和磁电效应的操纵和利用提供了全面而详细的参考。
Interface and size effects on electric/magnetic orders and magnetoelectric coupling are vital in the modern application of quantum-size functional devices based on multiferroic tunnel junctions. In order to give a comprehensive study of the interface and size effects, the properties of a typical asymmetric multiferroic tunnel junction, i.e., Fe/BaTiO3/Co, have been calculated using the first-principles simulations. Most importantly, all of the eight possible structures with four combinations of electrode/ferroelectric interfaces (i.e., Fe/BaO, Fe/TiO2, Co/BaO and Co/TiO2) and a series of barrier thicknesses have been taken into account. In this work, the equilibrium configurations, polarization, charge density, spin density and magnetic moments, etc., have been completely simulated and comprehensively analyzed. It is found that the ferroelectric stability is determined as a competition outcome of the strength of short-range chemical bondings and long-range depolarization/built-in fields. M/BaO (M = magnetic metal) terminations show an extraordinary enhancement of local polarization near the interface and increase the critical thickness of ferroelectricity. The bistability of polarization is well kept at the M/TiO2 interface. At the same time, the induced magnetic moment on atoms at the interfaces is rather localized and dominated by the local interfacial configuration. Reversing electric polarization can switch the induced magnetic moments, wherein atoms in M–O–Ti and M–Ti–O chains show preference for being magnetized. In addition, the difference between the sum of the interfacial magnetic moments is also enlarged with the increase of the barrier thickness. Our study provides a comprehensive and detailed reference to the manipulation and utilization of the interface, size and magnetoelectric effects in asymmetric multiferroic tunnel junctions.