Anisotropy of critical X-ray scattering in the vicinity of smectic B-nematic phase transition in EPPCB

• Published in: Solid state communications 1984-01, Vol.50 (8), p.757-761
• Main Authors: Pura, B., Milczarek, J., Przedmojski, J., Rajewska, A., Da̧browski, R.
• Format: Article
• Language: English
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/0038-1098(84)90980-3

The high-resolution X-ray scattering has been used to study the anisotropy of the density correlation function in the vicinity of S B-N phase transition in the recently developed material EPPCB. The effective critical exponents estimated in the temperature interval 10 −4 < t< 10 −2 ( t = T/ T C − 1) are: γ = 1.34 ± 0.09, ν ⊥ = 0.56 ± 0.08, ν | = 0.70 ± 0.06 and fulfill, within experimental errors, the relation γ = ν ⊥ + ν |. The novel feature is that the iso-intensity contours in the scattering plane containing the direction normal to the smectic layers have been found to be of four-winged shaped. A phenomenological (mean-field) theoretical approach explaining this shape in terms of the independence of fluctuations in the longitudinal (perpendicular to the smectic layers) and transversal (in the smectic planes) directions has been proposed.