论文标题
多效FECR2S4的磁电特性和低能激发
Magneto-electric properties and low-energy excitations of multiferroic FeCr2S4
论文作者
论文摘要
我们在频率范围0.3-3〜THz的多晶Fecr2s4的多效基态下报告了低频光激发，并且在应用最多7〜t的外部磁场时进行了变化。在轨道订购温度T_OO = 9K下方的基态下，我们观察到几种新模式的外观。通过将外部磁场平行并垂直于THZ辐射的繁殖方向，我们可以确定最强的吸收是主要是电偶极子的起源。我们将这些模式作为四面体环境中的Fe^{2+}离子（3D^6，s = 2）的低能电子激发。这些吸收系的特征频率和相对强度通过我们的计算令人满意地复制，假设在Fe^{2+} - 离子位点的有效交换场为12.8 cm-1。发现交换场的方向略微从AB平面中倾斜。通过我们的方法，我们还可以描述Mössbauer研究的先前报道的结果以及由轨道和非连接旋转顺序引起的电化极化的数量级。
We report on the low-frequency optical excitations in the multiferroic ground state of polycrystalline FeCr2S4 in the frequency range 0.3-3~THz and their changes upon applying external magnetic fields up to 7~T. In the ground state below the orbital-ordering temperature T_OO=9K we observe the appearance of several new modes. By applying the external magnetic field parallel and perpendicular to the propagation direction of the THz radiation, we can identify the strongest absorptions to be of predominantly electric-dipole origin. We discuss these modes as the low-energy electronic excitations of the Fe^{2+} ions (3d^6, S=2) in an tetrahedral environment. The eigenfrequencies and relative intensities of these absorption lines are satisfactorily reproduced by our calculation assuming an effective exchange field of 12.8 cm-1 at the Fe^{2+}-ions sites. The direction of the exchange field is found to be slightly tilted out of the ab-plane. With our approach we can also describe previously reported results from Mössbauer studies and the order of magnitude of the electric polarisation induced by orbital and non-collinear spin ordering.
