论文标题
Zn Doped Fe $ _ {2} $ MO $ $ _3 $ o $ $ _8 $中的磁性和振动THZ激发
Magnetic and vibronic THz excitations in Zn doped Fe$_{2}$Mo$_3$O$_8$
论文作者
论文摘要
我们在多种订购的阶段报告多表象Fe $ _ {1.86} $ Zn $ _ {0.14} $ MO $ $ $ _3 $ o $ $ _8 $在10-130 cm $ $ $^{ - 1} $（0.3-3.9 thz）的磁性激发阶段。在有限磁场中，在有限的磁场中观察到了$ t_n = 50 $ 〜k十一的光学主动模式的抗铁磁相，假设最低的lying模式是双重变性的。大量模式反映了比纯Fe $ _ {2} $ mo $ $ _3 $ o $ $ _8 $更复杂的磁性结构，或者除了通常的旋转式预训练模式之外，旋转拉伸模式也变得活跃。它们的磁场依赖性是沿易于轴施加的磁场，反映了从抗铁磁基层状态到铁磁性状态的不可逆磁场驱动的相变，而模式的数量在覆盖频率区域中保持不变。我们通过研究所有极化构型并确定了磁性和电动 - 偶极运动模式来确定某些AFM模式的选择规则。除了这些尖锐的共振外，不受外部磁场影响的广泛电动偶极激活兴奋带的发生在$ t_n $以下，发作为12 cm $^{ - 1} $。我们能够将此吸收带模型为与四面体环境中最低的fe $^{2+} $电子状态有关的振动激发。
We report on optical excitations in the magnetically ordered phases of multiferroic Fe$_{1.86}$Zn$_{0.14}$Mo$_3$O$_8$ in the frequency range from 10-130 cm$^{-1}$ (0.3-3.9 THz). In the collinear easy-axis antiferromagnetic phase below $T_N=50$~K eleven optically active modes have been observed in finite magnetic fields, assuming that the lowest-lying mode is doubly degenerate. The large number of modes reflects either a more complex magnetic structure than in pure Fe$_{2}$Mo$_3$O$_8$ or that spin stretching modes become active in addition to the usual spin precessional modes. Their magnetic field dependence, for fields applied along the easy axis, reflects the irreversible magnetic-field driven phase transition from the antiferromagnetic ground state to a ferrimagnetic state, while the number of modes remains unchanged in the covered frequency region. We determined selection rules for some of the AFM modes by investigating all polarization configurations and identified magnetic- and electric-dipole active modes as well. In addition to these sharp resonances, a broad electric-dipole active excitation band, which is not influenced by the external magnetic field, occurs below $T_N$ with an onset at 12 cm$^{-1}$. We are able to model this absorption band as a vibronic excitation related to the lowest-lying Fe$^{2+}$ electronic states in tetrahedral environment.
