Electromagnon excitation in the field-induced noncollinear ferrimagnetic phase of Ba2Mg2Fe12O22 studied by polarized inelastic neutron scattering and terahertz time-domain optical spectroscopy
Electromagnon excitation in the field-induced noncollinear ferrimagnetic phase of Ba2Mg2Fe12O22 studied by polarized inelastic neutron scattering and terahertz time-domain optical spectroscopy
复制标题
DOI：
10.1103/physrevb.93.035119
复制
发表时间：
2016-01-19
影响因子：
3.7
通讯作者：
Arima, Taka-hisa
中科院分区：
文献类型：
--
作者：
Nakajima, Taro;Takahashi, Youtarou;Arima, Taka-hisa
利用极化非弹性中子散射（PINS）和太赫兹（THz）时域光谱研究了Ba 2 Mg 2Fe 12 O22非共线公度亚铁磁相的磁场激发.先前的THz光谱研究报告了场诱导相表现出能量为约5 meV的电偶极活性激发[Kida等人，Rev. B 83，064422（2011）]。在目前的PINS测量中，我们观察到非弹性散射信号约5 meV的区域中心的自旋翻转通道。这直接表明电偶极激发确实是磁源，即电磁振子。此外，目前的太赫兹光谱证实，激发有振荡的极化平行于c轴。根据自旋电流模型（Katsura-Nagaosa-Balatsky模型），场致相的非共线磁序可以诱导垂直于c轴的静态极化，但不能诱导沿着c轴的动态极化.我们认为，电磁振子激发可以解释应用磁致伸缩模型的磁矩，这是从目前的实验结果推导出的异相振荡。
We have studied magnetic excitations in a field-induced noncollinear commensurate ferrimagnetic phase of Ba2Mg2Fe12O22 by means of polarized inelastic neutron scattering (PINS) and terahertz (THz) time-domain optical spectroscopy under magnetic field. A previous THz spectroscopy study reported that the field-induced phase exhibits electric-dipole-active excitations with energies of around 5 meV [Kida et al., Phys. Rev. B 83, 064422 (2011)]. In the present PINS measurements, we observed inelastic scattering signals around 5 meV at the zone center in the spin-flip channel. This directly shows that the electric-dipole-active excitations are indeed of magnetic origin, that is, electromagnons. In addition, the present THz spectroscopy confirms that the excitations have oscillating electric polarization parallel to the c axis. In terms of the spin-current model (Katsura-Nagaosa-Balatsky model), the noncollinear magnetic order in the field-induced phase can induce static electric polarization perpendicular to the c axis, but not dynamic electric polarization along the c axis. We suggest that the electromagnon excitations can be explained by applying the magnetostriction model to the out-of-phase oscillations of the magnetic moments, which is deduced from the present experimental results.