Experimental study of a SmA*-SmCA* phase transition

We have performed a detailed experimental study of the electroclinic behavi our in the SmA* phase above a SmA*-SmCA* phase transition. The tilt angle a nd polarization were measured as a function of the applied a.c. electric fi eld. and the dielectric constant was obtained under different values of the bias field (0 less than or equal to E-d.c. less than or equal to 3 V mum(- 1)). In the region of linear regime, the behaviour observed for this SmA*-S mCA* phase transition is very similar to the one previously described for S mA*-SmC* phase transitions. The experimental results obtained under high bi as field are in good agreement with the predictions of the simple theoretic al model considered.