Magneto-optical Properties Of Nanostructured Magnetic Fluid And Its Applications On Advanced Optical Materials Devices

Magnetic fluid is a kind of nanostructured material possessing magnetism. It is a novel functional material in optical field, which has both the fluidity of liquid and the tunable optical properties. This dissertation is mainly concerned with the magneto-optical properties of nanostructured magnetic fluid and its potential applications in photonic devices and materials.We first make a comprehensive introduction on magnetic fluid concerning its development history, main types and research progress. Then, we introduce its magneto-optical properties and its potential applications in photonic devices. One of the most important reasons that magnetic fluid may has these properties and applications is that when a magnetic field is applied parallel to the plane of a magnetic fluid thin film, magnetic chains form in the same direction as the magnetic field. As a result, we carry out experiments to study the agglomeration of magnetic particles in magnetic fluid. In addition, the dichroism is also one of the important magneto-optical properties of magnetic fluid. Experimental studies have shown that optical absorption rates are different for different deflection state of magnetic fluid under an external magnetic field.Based on the properties above, scientists have developed many magnetic fluid based photonic devices. Because the optical transmission of MF greatly influences the properties and the efficiency of these photonic devices, it is worth researching the optical transmission of MF under different conditions. We carried out experiments to investigate the temperature dependence of the optical transmission. In conclusion, the effect of thermal agitation is enlarged by rising the temperature when the amplitude of the magnetic field is unchanged, which suppresses the magnetic chains that are formed. Thus, the optical transmission is enlarged. From a theoretical analysis, we see that the transmittance fits an exponential growth with the ambient temperature around the MF, which is in good agreement with the experimental results. After the analysis of its sensitivity, it is known that this temperature sensor designed is suitable for using in higher temperature, to say above 60oC. When the magnetic fluid is irradiated by a laser beam, a part of the energy of the laser beam will be absorbed by the magnetic fluid for it has a relative large coefficient. For this reason, optical magnetic nanostructures, based on anodic aluminum oxide membranes and magnetic fluids, were fabricated and investigated in both transmission and magneto-optical properties. A strong enhancement in transmission property has been found compared with the traditional magnetic fluids. Excellent magneto-optical characteristic was obtained: a negative differential magnetic linear dichroism was observed, quite different from the traditional Langevin type of magnetic fluids. This phenomenon was interpreted by an antiferromagnetic coupling between two types of magnetic grains having different average diameters in the nanocomposites. Based on its outstanding magneto-optical effects, it may open potentials for future integral optical devices.