强磁场驱动的铁电相及物理效应研究

由于多种铁性序参量共存并相互耦合，磁致多铁材料展现出丰富的物理性质和重要的应用前景，是当前研究的热点。外加磁场能直接与这类材料中的自旋相互作用，产生特殊的磁有序结构，从而诱导出新的铁电相。特别是，强磁场驱动的铁电相往往呈现出新奇的物理效应，不同于低场或基态的铁电相。基于前期调研，我们分别在DyMnO3和Co2V2O7单晶中第一次发现了高场铁电相。本项目计划利用脉冲强磁场实验条件，对RMnO3(R=Sm,Eu,Gd,Tb,Dy,Ho)和R2V2O7(R=Ni,Co)系列单晶材料开展深入研究。一方面，我们希望在近邻体系中探测到类似的高场铁电相和发现新奇的物理效应；另一方面，我们将通过各种调控手段，揭示高场铁电相的物理本质，建立高场与低场铁电相之间的关联。通过本项目研究，希望澄清第II类多铁中的某些物理问题，探索极端条件下的新物态和新现象，为寻找新型应用多铁材料提供理论基础。

Owing to coexistence of two or more ferroic orders and their couplings, multiferroic material with magnetism origin exhibits intriguing physical properties and important applications, which is now a hot topic in material science. External magnetic field can interact with spins in the material directly and result in peculiar magnetic structures, leading to new ferroelectric phases. Particularly, the ferroelectric phase induced by a high magnetic field is sometimes quite different from that in a low field or magnetic ground state. Based on our preliminary investigation, we observe novel high-field ferroelectric phases in DyMnO3 and Co2V2O7 single crystals for the first time. In the present project, we propose to deeply study RMnO3(R=Sm,Eu,Gd,Tb,Dy,Ho) and R2V2O7(R=Ni,Co) series single crystals by pulsed high magnetic fields. We expect to explore high-field induced ferroelectric phase and related effects in similar compounds. By means of various experimental techniques, we wish to reveal the underlying physics of the high-field phase and establish a correlation between it and the low-field ferroelectric phase. Through this project, we will elucidate some long-standing issues in type II multiferroics. Further, we wish to uncover emergent phenomena and exotic states in extremely conditions, and improve knowledge for search of functional multiferroic materials.