Europhys. Lett.
Volume 74, Number 1, April 2006
Page(s) 22 - 28
Section General
Published online 22 February 2006
Europhys. Lett., 74 (1), pp. 22-28 (2006)
DOI: 10.1209/epl/i2005-10497-y

Critical Casimir effect in $\chem{^3He}$- $\chem{^4He}$ films

A. Maciolek1 and S. Dietrich2, 3

1  Institute of Physical Chemistry, Polish Academy of Sciences Kasprzaka 44/52, PL-01-224 Warsaw, Poland
2  Max-Planck-Institut für Metallforschung - Heisenbergstr. 3 D-70569 Stuttgart, Germany
3  Institut für Theoretische und Angewandte Physik, Universität Stuttgart Pfaffenwaldring 57, D-70569 Stuttgart, Germany

received 14 November 2005; accepted in final form 3 February 2006
published online 22 February 2006

Universal aspects of the critical Casimir force fC in wetting films of $\chem{^3He}$- $\chem{^4He}$ mixtures near their bulk tricritical point are studied within models of the corresponding universality class. fC for such films of thickness L is calculated along isotherms at several fixed concentrations of $\chem{^3He}$. Nonsymmetric boundary conditions impose nontrivial concentration profiles leading to repulsive force which exhibit a rich crossover behavior between the tricritical point and the line of critical points. The theoretical results agree semiquantitatively with published experimental data and emphasize the importance of logarithmic corrections. The universal Casimir amplitude is the amplitude of the leading behavior $\sim L^{-3}(\ln L)^{1/2}$ dominating the contribution $\sim L^{-3}$ whose amplitude is nonuniversal and which is comparable with the background dispersion force contributions.

05.70.Jk - Critical point phenomena.
64.60.Kw - Multicritical points.
68.15.+e - Liquid thin films.

© EDP Sciences 2006