Research Laboratory for Quantum Materials, Singapore University of Technology and Design , Singapore 487372, Singapore.
Department of NanoEngineering, University of California , San Diego, 9500 Gilman Drive, Mail Code 0448, La Jolla, California 92093-0448, United States.
ACS Appl Mater Interfaces. 2017 Jan 18;9(2):1899-1906. doi: 10.1021/acsami.6b13183. Epub 2017 Jan 5.
Novel phenomena appear when two different oxide materials are combined together to form an interface. For example, at the interface of LaAlO/SrTiO, two-dimensional conductive states form to avoid the polar discontinuity, and magnetic properties are found at such an interface. In this work, we propose a new type of interface between two nonmagnetic and nonpolar oxides that could host a magnetic state, where it is the ferroelectric polarization discontinuity instead of the polar discontinuity that leads to the charge transfer, forming the interfacial magnetic state. As a concrete example, we investigate by first-principles calculations the heterostructures made of ferroelectric perovskite oxide PbTiO and nonferroelectric polarized oxide TiO. We show that charge is transferred to the interfacial layer forming an interfacial ferromagnetic ordering that may persist up to room temperature. Especially, the strong coupling between bulk ferroelectric polarization and interface ferromagnetism represents a new type of magnetoelectric effect, which provides an ideal platform for exploring the intriguing interfacial multiferroics. The findings here are important not only for fundamental science but also for promising applications in nanoscale electronics and spintronics.
当两种不同的氧化物材料结合在一起形成界面时，会出现新的现象。例如，在 LaAlO/SrTiO 的界面上，会形成二维导电态以避免极性不连续性，并且在这种界面上会发现磁性。在这项工作中，我们提出了一种新的非磁性和非极性氧化物之间的界面，该界面可以承载磁性状态，其中导致电荷转移并形成界面磁性状态的是铁电极化不连续性，而不是极性不连续性。作为一个具体的例子，我们通过第一性原理计算研究了由铁电钙钛矿氧化物 PbTiO 和非铁电极化氧化物 TiO 组成的异质结构。我们表明，电荷会转移到界面层中，形成界面铁磁有序，这种有序可能会持续到室温。特别是，体铁电极化和界面铁磁性之间的强耦合代表了一种新型的磁电效应，为探索有趣的界面多铁性提供了理想的平台。这些发现不仅对基础科学很重要，而且对纳米尺度电子学和自旋电子学的有希望的应用也很重要。
