Dynamic Faraday magneto-optical properties of the water-based Fe3O4 magnetic fluids

Dynamic properties of water-based Fe3O4 magnetic fluids are investigated in AC magnetic field. The magnetic fluid films with 6µm thick are implemented in magneto-optical rotation effect by self-designed experimental platform. The transmitted light intensity of magnetic fluids diluted into different mass percentage concentration are presented and compared with magneto-optical glass. A new property of Faraday effect of magnetic fluid is reported as double frequency, i.e. the response frequency of magnetic fluids is twice of the frequency of the modulating magnetic field. The detailed results show that the asymmetry of output corresponding to the positive half period and the negative one aggravates for large angel between the light axes of the polarizer and the analyzer. The response of Faraday effect decreases for the denser or diluter magnetic fluids than 10% mass concentration. These dynamic properties can be interpreted by introducing the friction force among magnetic nanoparticles.