Chemistry:Paranematic susceptibility

In the study of liquid crystals the paranematic susceptibility (Latin: susceptibilis "receptiveness") is a quantity that describes the degree of induced order in a liquid crystal in response to an applied magnetic field. As a result of the diamagnetic anisotropy of liquid crystal molecules, nematic order can be produced by the application of a magnetic field. If a magnetic field is applied to a nematic liquid crystal in the isotropic phase then the order is given by:

[math]\displaystyle{ \langle P_2\rangle=\eta\mathbf{H}^2 }[/math]

The proportionality constant [math]\displaystyle{ \eta }[/math] is the paranematic susceptibility. The value increases as the liquid crystal is cooled towards its transition temperature. In both the mean field approximation and Landau-deGennes theory the paranematic susceptibility is proportional to [math]\displaystyle{ (T-T^*_C)^{-1} }[/math] where [math]\displaystyle{ T^*_C }[/math] is the transition temperature.

References

• E.B. Priestley, P.J. Wojtowicz, and P. Sheng, Introduction to Liquid Crystals, Plenum Press, 1974. ISBN:0-306-30858-4
• Sheng, Ping; Wojtowicz, Peter J. (1976-11-01). "Constant-coupling theory of nematic liquid crystals". Physical Review A (American Physical Society (APS)) 14 (5): 1883–1894. doi:10.1103/physreva.14.1883. ISSN 0556-2791. http://repository.ust.hk/ir/bitstream/1783.1-52237/1/PhysRevA.14.1883.pdf.