Size effects in [N(CH3)4]2Zn0.58Cu0.42Cl4 crystals

The temperature dependences of birefringence in thin [N(CH 3 ) 4 ] 2 Zn 0.58 Cu 0.42 Cl 4 crystals in the thickness range 20 × 10 −6 ≤ d ≤ 500 ↾ 10 −6 m have been investigated. An increase in the temperatures of the parent phase-incommensurate phase and incommensurate phase-ferroelectric phase transitions has been found. The reasons for the shift in the phase transition temperatures with a decrease in the thickness of [N(CH 3 ) 4 ] 2 Zn 0.58 Cu 0.42 Cl 4 crystal and the size effect in crystals with an incommensurate superstructure are discussed.