基于化学诱导相变法的磁性液体合成及其磁光效应
Synthesis of Ferrofluids Based on Chemically Induced Transition and Their Magneto-Optical Effects

使用化学诱导相变法制备的γ-Fe₂O₃磁性纳米颗粒，经油酸表面包裹可分散于煤油中合成磁性液体.在磁场作用下，圆偏振光透过磁性液体样品后，由于双折射效应和二向色性，透射光为椭圆偏振光.用圆偏振光作为探测光源，使用θ扫描技术可得到透射椭圆偏振光的相对强度角分布的T-θ曲线.从曲线可得到反映透射椭圆偏振光特征的相对透射强度的最小值T_min和最大值T_max以及椭圆的取向角Δθ.从这些透射光的参数可导出磁双折射效应Δn和磁二向色性Δκ.实验结果表明：随着磁场H增强或颗粒体积分数？_v增大，Δn和Δκ增加.所制备的磁性液体的磁双折射和磁二向色性来源于在磁场作用下，磁性液体中的磁性纳米颗粒由分散体系形成了场致链结构.
Magnetic nanoparticles of γ-Fe₂O₃ prepared with the method of chemically induced transition and wrapped in a layer of membrane-like surface with oleic acid can be dispersed in kerosene to synthesize ferrofluids. When a circularly polarized light travels through a ferrofluid sample in the presence of an external magnetic field, magnetic birefringence and magnetic dichroism effects cause the transmitted light to behave as an elliptically polarized light. Using circularly polarized light as the illumination source and the θ-scan technique, a T-θ curve with the angular distribution of relative intensity for the transmitted light, which corresponds to elliptically polarized light, is obtained. From the T-θ curve, the T_min, T_max of relative transmission strength and the orientation angle (OA) of the ellipse Δθ can be obtained. According to these parameters, information of the magnetic birefringence Δn and the dichroism Δκ can be deduced. Experimental results indicate that both Δn and Δκ increase with the applied magnetic field strength or the particle's volume fraction in the ferrofluids. For the ferrofluids, the magnetic-optical effects result from the formation of a chain-like structure from the dispersed particle system under the external magnetic field