双偶氮苯掺杂液晶在磁场下的Freedericksz转变

Magnetic-Field-Induced Freedericksz Transition of a Nematic Liquid Crystal Doped with Double Azo

发现掺有机杂质(双偶氮苯)的沿面排列丝状液晶与纯液晶相比,会显著减低在静磁场下发生Freedericksz转变的阈值.而传统的方法则是通过掺入微细的铁粉来降低阈值.这一新现象主要是由于双偶氮苯具有较强的磁化率各向异性,从而导致掺杂液晶的有效磁化率各向异性增大.理论推导的双偶氮苯磁化率各向异性常数要比纯5CB大2个数量级.Freedericksz转变阈值的减低对研究磁场下的非线性光学效应有重大的意义.

The Freedericksz transition induced by a perpendicular static magnetic field of a planar alignment nematic liquid crystal doped with little organic dopant (double azo) was studied.It was observed for the first time that the doped 5CB will dramatically decrease the critical magnetic field compared to the pure 5CB while the conventional solution is doping ferro paticles to decrease the critical magnetic field The results show that in the guest host system, the guest double azo has much larger diamagnetic susceptibility anisotropy than pure 5CB and will drag the 5CB molecule to reorientation under the lower magnetic field