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:

$\langle P_{2}\rangle =\eta \mathbf {H} ^{2}$

The proportionality constant $\eta$ 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 $(T-T_{C}^{*})^{-1}$ where $T_{C}^{*}$ 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. 14 (5). American Physical Society (APS): 1883–1894. doi:10.1103/physreva.14.1883. ISSN 0556-2791.