Phase transition and excess specific heat in RS-ARS mixed crystals

Abstract The specific heat of Rochelle salt–ammonium Rochelle salt (RS 1− x –ARS x ) mixed crystals for 0.18⩽ x ⩽0.9 (region III) exhibits a finite jump at the transition to the ferroelectric phase. Any critical behaviour like diverging is not observed. We consider the behaviour of the specific heat around the transition on the basis of Landau theory taking account of fluctuation effects. We also give a consideration from a structural point of view.