高转变温度双钙钛矿型氧化物薄膜和异质结的制备与磁电耦合研究

因其丰富的物理内涵和广泛的应用背景，多铁材料的磁电耦合效应是近年来材料领域的一个持续研究热点。利用室温多铁性和铁磁性氧化物合成全氧化物异质结，是实现室温强磁电耦合及良好稳定性的途径之一。目前多铁性全氧化物异质结受限于低的耦合阻断温度。因而，发掘更多具有高居里温度的铁磁（亚铁磁）氧化物，并探索其在多铁异质结中的应用，具有重要的科学价值。受此启发，本课题将系统地研究具有高居里温度的双钙钛矿型磁性氧化物薄膜，及其与多铁材料铁酸铋形成的异质结。我们首先将通过优化生长工艺来制备高质量的双钙钛矿氧化物外延薄膜，重点探索在超薄厚度实现室温亚铁磁性的方法。进而我们将制备双钙钛矿氧化物与铁酸铋的异质结，结合宏观和微观表征方法及理论计算去厘清界面多自由度的耦合关联与重构。最后，我们将研究铁电极化对界面电子结构和磁性重构的影响及机理，探索实现室温电控磁性的途径。这一研究有望为多铁性研究提供一个新的范例。

Due to the wide range of physical insights and promising functionalities, multiferroics and the associated magnetoelectric coupling have attracted intense research interests in both materials science and condensed matter physics research over past decades. All-oxide heterostructures, comprised of multiferroic oxides and ferro- (ferri-) magnetic oxides, provide ideal candidates to realize strong magnetoelectric coupling with excellent stability at room temperature. However, so far, the blocking temperatures of many all-oxide multiferroic heterostructures are below room temperature, limiting further developments. Therefore, it is highly demanded to investigate other ferro- (ferri-) magnetic oxides with a higher Curie temperature (Tc), as well as how they can be used in multiferroic heterostructures. Here, we propose to systematically study thin films of double-perovskite oxides that have the Tc higher than room temperature, as well as their heterostructures with multiferroic BiFeO3 (BFO). By optimizing the deposition procedure, we will first fabricate high quality epitaxial films of double-perovskite oxide Sr2FeMoO6 (SFMO). We will investigate the routes to stabilize ferrimagnetic state with a high saturation magnetization at room temperature in ultrathin SFMO films. Next, we will synthesize heterostructures comprised of BFO and SFMO with high quality interfaces. By combing multiple characterization methods that probe the materials at different length scales along with theoretical calculations, we will reveal the couplings between charge, spin, orbital and lattice degrees of freedom at the interfaces. Last, we will study how the ferroelectric polarization of BFO affects the electronic and magnetic reconstructions in the heterostructure, to shed light on the routes to realize electric field control of magnetism at room temperature. Our proposed study might provide a new paradigm to study multiferroic and magnetoelectric coupling.