Low frequency elastic behaviour of (NH₄)₄LiH₃(SO₄)₄ (ALHS): Ferroelastic domain freezing and static stress dependence

Abstract

Distinct anomalies have been found in the temperature dependence of the low-frequency elastic compliance of ferroelastic ALHS, which are connected to the motion of domain walls. Around T_f ≅ 162 a distinct lowering of domain wall mobility occurs (partial ‘'domain freezing'') leading to an increase of the storage modulus and to a maximum of the loss modulus. Below T_f the loss modulus exhibits and additional maximum which is related to domain wall motion, too. In addition, it was observed that the elastic behaviour of a crystal of ALHS is dependent on the ‘'history'’ of the given sample affecting as well the domain wall motion between T_c and T_f as the low temperature relaxation (T < ⟨i⟩T_f) in particular. Besides, the elastic behaviour of ALHS has been studied for various values of static stress up to several MPa.