通过磁光效应研究磁性液体在外场下的颗粒成链现象

Using magneto-optical effect to study the chain aggregation behavior of ferrofluids under an external magnetic field

在对磁性液体的磁光效应的理论分析与实验测量的基础上讨论了其在磁场下的各向异性现象.首先,通过电磁理论对成链的各向异性介质模型的介电张量形式进行了一般性的分析,然后,基于磁性液体的微观理论模型讨论了磁性液体在外加磁场下出现凝聚成链的行为.基于上面的结果,我们将实验可观测量——两种传输模式的折射率差和不同颗粒数的链(长度不同的链)的比例以及磁场强度建立联系.最后,在实验上探测了磁性液体薄膜的透射光偏振状态变化随外磁场的变化,并对测得的数据进行计算机拟合分析,验证了不同长度的链的数目之间的比例关系.

In this paper, we discuss the field-induced inhomogeneity in ferrofluids based on our theoretical analysis and experimental measurement. First, the dielectric tensor of the anisotropic media with particle chain is analyzed by using the electromagnetic theory. Second, based on a microscopic model, we discuss the behavior of the chain aggregation in the ferrofluids under external magnetic fields. Then, we relate the observable quantity-refraction index differences of the two propagating modes to the ratio between chains of different sizes and the strength of magnetic field. Finally, we experimentally measure the magneto-optical effect of ferrofluids by detecting polarization state change of the laser passing through the ferrofluids film, and the ratio between chains of different sizes is obtained by using computer simulation.