Mixtures of a polar solute 4-n-pentyl-4'-cyanobiphenyl in a non-polar
nematic solvent exhibit two separated low frequency dielectric relaxat
ions for concentrations of the solute between 2 mol% and 20 mol% over
a limited temperature range. This behaviour is attributed to coexistin
g nematic and smectic B phases, in which the polar solute probe has di
fferent relaxation frequencies. The observed dielectric spectra can be
accurately fitted to two Debye-like relaxations, and the strengths of
the absorptions are proportional to the amounts of the coexisting pha
ses. A microscopic determination of the phase diagram confirms the ass
ignment of the coexisting phases, and it is concluded that there is a
preference of the dipolar probe molecule for the smectic B phase, whic
h is induced as a result of solute-solvent interactions.