Investigation of magneto-electric optical effect

我们研究了新的磁光效应，即“磁电光效应”和“磁手征效应”。在这些光学效应中，去偏振光的光学响应取决于传播子矢量的方向。我们研究了亚铁磁体、GaFeO_3和尖晶石型Fe_3 O_4单晶的光学特性，以阐明磁电光效应和磁手征效应的机制。GaFeO_3在低温下具有自发磁化和极化，表明空间反转对称性和时间反转对称性的破坏，而Fe_3O_4具有局域空间反转对称性。在1.0- 2.5eV的能量范围内，研究了极性亚铁磁体GaFeO_3的光吸收随光传播方向反转的变化。此外，我们还发现了一种新的磁光效应，称为X射线非互易定向二向色性，即在Fe离子的K边缘附近的X射线吸收取决于X射线传播矢量是否平行或反平行于GaFeO 3中的磁化和电极化矢量的外部产生。这些光学响应表现出明显的极化和磁化强度依赖性，表明这些光学效应与环矩之间的关系。本文所展示的X射线非互易定向二向色性光谱可以作为一种有用的工具来证明非中心对称系统中的局域磁性，如磁干扰和纳米结构。不仅在GaFeO_3中，而且在Fe_3 O_4中也发现了X射线非互易定向二向色性。

We have investigated the new magneto-optical effects termed "magneto-electric optical effect" and "magneto-chiral effect". In these optical effects, the optical response of the depolarized light depends on the direction of the propagator vector. We studied the optical features in the single crystals of the ferrimagnet, GaFeO3, and spinel-type Fe3O4 in order to clarify the mechanism of the magneto-electric optical effect and magneto-chiral one. GaFeO3 has spontaneous magnetization and electric polarization at low temperatures, indicating the breakdown of the space inversion symmetry and the time reversal one, while Fe3O4 has local space inversion symmetry.The magneto-electric optical effect, i.e., the change of optical absorption upon the reversal of the light propagation direction, has been investigated for the polar ferrimagnet GaFeO3 in the energy region of 1.0-2.5 eV. Moreover, we have found a novel magneto-optical effect, termed x-ray nonreciprocal directional dichroism, that the x-ray absorption at around the K edge of an Fe ion depends on whether the x-ray propagation vector is parallel or antiparallel to the outer production of the magnetization and electric-polarization vectors in GaFeO3. These optical responses show the obvious dependence on the electric polarization and magnetization, suggesting the relationship between these optical effects and the toroidal moment. The x-ray nonreciprocal directional dichroism spectroscopy as demonstrated here can be a useful tool to prove the local magnetism in noncentroysymmetric systems such as magnetic interferences and nanostractures. We have found the x-ray nonreciprocal directional dichroism not only in GaFeO3 but also Fe3O4.