Abstract
In a frustrated binary mixture system of MC881 and MC452, where the border line between Sm$C_{A}^*$ and Sm$C^*$ in the temperature-concentration phase diagram runs almost parallel to the ordinate temperature axis, we have found a continuous change between them close to the critical concentration. The continuity has been confirmed as an intrinsic property in the bulk by observing almost perfect bell-shaped Bragg reflection bands due to the helicoidal director structure. The temperature variation of peak wavelength of the half-pitch band and, in particular, the characteristic disappearance of the full-pitch band apparently within the Sm$C^*$ temperature region have been simulated with a change in the ratio of ferroelectric and antiferroelectric orderings.
