层状复合材料的磁光耦合与圣维南原理

【作者】 罗小彬；

【导师】 张宁；

【作者基本信息】 南京师范大学 ， 物理电子学， 2014， 博士

【摘要】 自从在液体和气体中发现磁致双折射效应后距今已有100多年,1970年代某些磁性半导体在低温和强磁场条件下也被观察到具有磁致双折射效应。但由于使用不便,这些材料均无实际应用。由于室温和低磁场下的固体磁致双折射材料具有广泛的应用前景,因此寻求该类材料成为物理及材料领域的一个极具意义的研究方向。近年来层状复合功能材料的迅速发展为开拓层状复合磁光材料提供了思路。本文将磁致伸缩材料和弹光材料复合成一种新型的层状磁致双折射材料,在室温下观测到较大的磁致双折射效应,其磁光效应来源于磁致伸缩与应力双折射的乘积效应,或称为磁致伸缩诱导应力双折射效应。该复合材料由铁磁材料铽镝铁和高分子材料聚碳酸酯两相组成,前者具有超大磁致伸缩效应,而后者具有稳定的应力双折射功能。两者制成片状、并粘结后形成层状复合材料。本文首先分别讨论了两相材料各自的性质,并实验测量了相关参数；实验观测了两者层状复合结构的磁光效应及其规律；由铁磁体的本构方程和弹光相材料的应力应变方程出发,推导出该复合材料的磁致应力双折射效应的数学模型——归一化输出光强。通过Matlab对理论进行仿真显示,理论计算与实验结果趋于一致；然后从弹性力学基本方程出发,建立弹性力学模型,选择合适的边界条件,分析了弹性耦合条件下圣维南原理对弹光相介质内部应力分布的影响,对归一化输出光强表达式作出修正；最后对于该层状复合材料的应用进行尝试,将其用作磁光调制器,成功实现了低频信号(频率≤5kHz)的调制,再将其用作核心部件组建微位移测量系统,该测量系统预期精度可达1μm。更多还原

【Abstract】 More than100years have passed since the magneto-birefringence (MBR) effect was found in gas and liquid. Later, MBR effect was also found in some semiconductors at low temperature and strong magnetic field. But all of those materials were not utilized in reality due to inconvenience. So it is meaningful to seek solids that can show MBR effect at room temperature and low magnetic field. Recently laminate magneto-electric composites have been developed rapidly, which brings inspiration to fabricate laminate magneto-optical composites.In this paper, combining magnetostrictive material with elasto-optical medium, laminate magneto-optical composites were suggested and fabricated, which can show great MBR effect at room temperature. The MBR effect is based upon the product effect of magnetostriction and stress-birefringence. It provides a new idea to develop magneto-optical materials with high performance.Ferroalloy of rare-earth terbium dysprosium iron (TDF) and polycarbonate were selected as magnetostrictive phase material and elasto-optical phase material respectively. First, the properties of each phase materials were characterised and the relevant parameters were measured. Then, the magnetooptical effects of the laminate composites were observed. Second, combined the constitutive equation of magnetostrictive phase with the stress-strain equation of the elasto-optical phase, the formulation of the normalized intensity of emergent light (NIEL) was derived. Analysis showed that the theoretical results were in agreement with the experimental ones. Third, starting from the basic equations of elasticity, a elastic mechanical model was proposed and a set of appropriate boundary conditions were chosen to analyze the effect of Saint-Venant’s principle on the stress distribution in the elastic material under the condition of interfacial elastic coupling, then the formulation of NIEL was modified. At last, the applications of the laminate composites were explored, used the laminate composites as the magneto-optical modulator to implement modulation of low frequency signal (not higher than5kHz) successfully, and then used them as the core component of a micro-displacement measuring system. Experiments showed that the precision of the system can reach1μm.更多还原