Magneto-optical Effects Of Ferronematic Materials

Magnetic fluid (MF) is a kind of stable colloidal suspension of small magneticparticles with typical sizes of10nm. It is a novel functional material in optical field,which possess both the fluidity of liquids and the magnetism of solid magnetic materials.Because of the dramatic development of optical communication and integrated optics，the optical properties of MF have attracted a great deal of attention from researcherssince the late part of the20th century, which include tunable refractive index,birefringence, Faraday effect, optical transmittance, optical scattering and so on.The optical properties (birefringence and figure of merit of optical properties) ofthe pure MF and ferronematic thin films under externally applied magnetic field areinvestigated mainly in this treatise. The pure MF and the ferronematic samples show thesimilar magnetic-field-dependent properties of birefringence and figure of merit, whichincrease with the magnetic induction and tend to saturate at high field. Both types ofsamples with high volume fraction of magnetic particle have high birefringence.Besides, the ferronematic material with high volume fraction of5CB has relatively highvalue of Q under certain fixed field strength. The experimental results reveal that themagnetic particle concentration is crucial to the birefringence of the samples and5CBconcentration has no influence on the birefringence of the samples. However, the5CB iscrucial to the figure of merit of optical properties of the ferronematic samples andmagnetic particle concentration has no influence on the figure of merit of opticalproperties of the ferronematic samples. The Q values of the ferronematic materials arelarger than those of their counterparts (pure MFs). The maximum relative increase inQ value is around6.8%for our experimental samples.The optical transmittance of pure MF and ferronematic thin films as a function ofincident wavelength in the visible range are also investigated. The transmittances ofpure MF and ferronematic samples increase gradually with the incident wavelength anddecrease with the magnetic particle concentrations and thicknesses of the samples.Moreover, the transmittances of both kinds of samples increase slightly with themagnetic field strength at certain wavelength. For the ferronematic materials, thesample with high volume fraction of5CB has a relatively high transmittance. Themaximum relative enhancement of transmittance of our experimental samples isobtained to be around190%at the wavelength for500nm.