Papers by Author: Shu Fang Fu

Abstract: We present the sum-frequency (SF) generation of antiferromagnetic sandwich structure NM/AF/NM in the THz frequency field. In the geometry with the anisotropy axis parallel to the film surface and normal to the plane, using TE wave obliquely incident upon the film, we find that SF outputs is sensitively affected by the incident angle and the incident frequencies.

Abstract: The effect of magnetic fields on the molecular configuration of liquid crystalline polymers (LCPs) under simple shear flows is numerically simulated using the Doi theory when the initial state of the director is out-of-plane. A method of effectively enhance the order parameter is discussed in this paper. The simulation results show that the degree of molecular alignment can be greatly increased along the direction of the magnetic field. It is an efficient way to improve the performance of LCP materials.

Abstract: The reflectivity and transmission spectra will be discussed in an antiferromagnetic (AF) sandwich structure as ZnF₂/MnF₂/SiO₂. Such geometry is used, where the AF anisotropy axis and external static magnetic field both are parallel to the film surfaces and normal to the incident plane. The results show that the reflectivity and transmission spectra can be governed by the incident angles and the AF thickness.

Abstract: The reflection and transmission of antiferromagnetic sandwich (SiO2/MnF2/ZnF2), which impacted by third-order nonlinear modification from antiferromagnetic film (MnF2), is analyzed. The obvious effect on the reflection can be observed in the vicinity of the resonant frequency. In order to illustrate the influence of medium on the refection and transmission, the case air/MnF2/air also is considered.

Abstract: The effect of magnetic field on shear stress of disklike nematic liquid crystalline polymers (LCPs) is analyzed with the extended Doi theory in which the molecular shape parameter is defined at negative one. The evolution equation for the probability function of the LCP molecules is solved without any closure approximations. It can be seen that the shear rate regions of the sign changes of the time-averaged first normal stress differences are completely contrary with those conclusions achieved for the rodlike LCPs.

Abstract: The effect of magnetic field on the flow-phase diagram of discotic nematic liquid crystalline polymers (LCPs) is analyzed with the extended Doi theory in which the molecular shape parameter is defined at negative one. The evolution equation for the probability function of the LCP molecules is solved without any closure approximations. The transition among flow-orientation modes, such as tumbling, wagging and aligning defined similar to the rodlike LCPs, are strongly affected by the magnetic fields parallel to the flow direction.

Abstract: Stable water-based Fe3O4 ferrofluid was obtained by three steps. Fe3O4 nanoparticles with the size of about 10 nm were first prepared by chemical co-deposition method. In order to prevent Fe3O4 nanoparticles from agglomerating, they were coated by bilayer surfactants. Then, the coated Fe3O4 nanoparticles were dispersed well into water. Due to the actions of electrostatic force and hydrogen bond, the water-based Fe3O4 ferrofluids can keep stable for two years and no layered phenomenon occurred. The ferrofluid has high saturation magnetization, low remnant magnetization and coercive force.

Abstract: The effect of molecular shape on molecular configuration of liquid crystalline polymers under shear flows is numerically analyzed using the extended Doi theory. We can find that the molecular shape strongly affects on the transition among flow-orientation modes. The change in sign of the first normal stress difference is to speed up by the increasing .

Abstract: Nonlinear bulk polaritons in uniaxial antiferromagnetic film are investigated under a magnetic field that is along the anisotropy axial. The numerical calculations show that the nonlinear shift in frequency is very obvious. The antiferromagnetic film presents the strong anisotropy under the magnetic field.