基于强场太赫兹脉冲的新型六方RFeO3晶体非线性光磁效应研究

实现磁性材料自旋的超快调控，对超快信息存储与处理有重要意义。近年来，THz波对正交RFeO3晶体的超快光磁调控，取得一系列重要研究进展，被《Nature》等期刊多次报道。但要实现THz与自旋波强耦合和自旋极化翻转等非线性调控，必须借助自由电子激光等强场THz脉冲。最近，六方RFeO3被报道具有优异的室温磁电耦合特性，但其超快光磁特性和磁电耦合机理有待系统研究。特别是六方RFeO3晶体有一定亚稳性，更鲜有报道。本项目选取对THz有丰富响应特性的六方RFeO3晶体为研究对象，借助高平均功率THz-FEL在高功率、波长可调、窄线宽等方面优势，系统研究相干强场THz脉冲与六方RFeO3晶体的强耦合作用，探讨强场THz脉冲对该体系自旋极化的调控规律，揭示动态磁电耦合机理，阐明光-电-磁耦合作用下的非线性自旋调控物理机制，实现强场THz对自旋更高效的控制，为新型超快信息存储器件设计奠定基础。

The ultrafast control of electron spins in magnetic materials plays an important role for the rapid development of ultrafast information storage and processing. Recently, significant progress has been achieved for the ultrafast opto-magnetism of orthorhombic rare earth orthoferrite RFeO3, which has been reported at many prestigious journals, like Nature, etc. However, it is essential to employ the intense THz pulse, like free electron laser, to realize the strong coupling between THz and spin wave and the nonlinear control of spin reversal. Now, hexagonal RFeO3 has been reported to show magnetoelectric coupling at room temperature, which has gained increasing interests. While its ultrafast opto-magnetism and intrinsic magnetic-electric coupling mechanism are needed to be systematically explored. Especially, it is difficult to grow hexagonal RFeO3 crystals due to its metastable state. In this project, the ultrafast opto-magnetism and spin-related resonance of hexagonal RFeO3 crystals will be intensively investigated by the THz-FEL which shows advantages of high power, variable wavelength and narrow bandwidth. The strong coupling between intense THz pulse and hexagonal RFeO3 crystals, and the modulation of electron spins will be studied in order to reveal the dynamic magnetoelectric coupling. The mechanism of nonlinear spin control will be discussed based on the optical-electric-magnetic coupling within the system. Finally, the intrinsic spin dynamics of hexagonal RFeO3 crystals will be uncovered and more efficient control of spins by the intense THz pulse can be expected, which will greatly facilitate the design of novel ultrafast information storage devices in the future.