A homeotropical alignment nematic liquid crystal doped with FeTPPCl will dramatically decrease the critical magnetic field for the bend reorientationin a static magnetic field

The Freedericksz transition of homeotropical alignment liquid crystal doped with little FeTPPCl, which was induced by a perpendicular de magnetic fiel d, has been studied theoretically and experimentally in this paper. And the doped 5CB was observed to have dramatically decreased the critical magneti c field for bend reorientation, only one fourth of that needed for pure 5CB . This phenomenon is due to the intense paramagnetic of FeTPPCl [5,10,15,20 -Tetraphenylporphineiron(III) chloride] and the interaction between the hos t and guest in the form of the coordination of -CN in 5CB onto the metal io n of the porphyrino. However, 5CB doped with ZnTPP [5,10,15,20-Terraphenylp orphinezinc(II)] exhibited no decrease in the critical magnetic field. This result is very useful in liquid crystal display as magneto-optic component .