RMn2O5体系高温电控多铁性行为研究

Achieving near-room-temperature multiferroicity and tunability of magnetism/multiferroicity by electric field in the so-called Class II single-phase multiferroics (or magnetically induced ferroelectricity) are the most important potential applications of multiferroics, which therefore has always been a challenging topic. On basis of the mechanism that the symmetric exchange striction in some collinear spin systems breaks the spatial inversion symmetry, quite larger polarization as well as strong magnetoelectric coupling were found in typical RMn2O5 family. Nevertheless, previous works show lots of mutual "contradictory" results, indicating that the multiferroic physics of RMn2O5 has not yet been effectively demonstrated and few attentions have been paid on the physical phenomena in high-temperature range. Proceeding from the research actuality of RMn2O5, this proposal focuses on the thermodynamic phase transition, magnetic and multiferroic properties related to temperature or electric field, and studies on the tunability of multiferroicity by high-temperature electric field. With detailed experimental characterizations and theoretical analysis, the microscopic physical mechanism of electronically controlled multiferroic properties shall be revealed. And on this basis, high-quality thin films will be prepared to further explore the tunability of multiferroicity by high-temperature electric field and possible near-room-temperature electrically controlled new effects. This proposal can help better understanding of the microscopic physics in Class II multiferroics and lay a solid foundation for the potential application of electrically controlled magnetism/multiferroicity.

在第II类单相多铁(磁致多铁)中实现近室温多铁性及电控磁性/多铁性，是多铁性功能最重要的潜在应用，也因此一直是一项具有挑战性的课题。特定共线自旋系统中的对称交换伸缩效应能够破坏空间反演对称，基于此机制，人们在典型体系RMn2O5中发现了较大的铁电极化以及强磁电耦合。然而，过往的研究工作展示了很多相互“矛盾”的结果，该体系的多铁性物理仍未被有效昭示，特别是高温区的物理现象缺乏关注。本项目申请从RMn2O5体系的研究现状出发，集中关注热力学相变、磁性和多铁性等对温度与电场的响应，研究高温区极化电场调控多铁性行为。通过细致的实验表征与理论分析，揭示RMn2O5体系电控多铁性的微观物理机制，并以此为基础，制备高质量薄膜以深入探索电控多铁性，发掘可能存在的近室温电场调控新效应。本项目申请有助于更好地理解第II类多铁性材料中的微观物理，为实现电控磁性/多铁性的潜在应用价值奠定基础。

在磁电材料中实现电控磁性/多铁性乃至磁电调控，一直受到研究者的广泛关注。为了揭示和丰富典型第II类多铁性体系以及磁电体系中深刻的物理内涵，本项目对体系RMn2O5和其他磁电耦合材料的设计合成和物理性质表征进行了深入研究。虽然具体的研究体系、方法和具体方案上与实际施行有一定的差别，但是在关键科学问题上却保持基本一致，取得了一系列的研究进展，完成了核心目标。首先，通过提出一种有别于传统的热释电测量方法，详尽研究了GdMn2O5中高温区极化电场调控低温多铁性的可能性；同时，深入研究了共线反铁磁结构的NdCrTiO5中磁场对电极化的调控与电场对磁矩的调控，为寻找新的磁电耦合材料提供了研究方向。在此基础上，又陆续设计合成了Sm2BaCuO5、Co3NiNb2O9等化合物，并深入研究了其磁电调控特性，为电控磁性/电控多铁性提供了坚实的物理基础。本项目的开展，可以提供新的电场调控磁性/多铁性方法，丰富了磁电耦合与调控的研究内容，进一步促进了磁电材料的发展。共发表研究论文6篇，包括Applied Physics Letters(2)、Journal of Materiomics(1)、Chinese Physics B(1)、RSC Advances(1)和Ceramics International(1)。在本项目的资助或支持下，共有3位硕士研究生获得硕士学位。