Peculiarities of PMN structure below temperature of relaxor phase transition

The results of investigations of PMN single crystal atomic structure at temperatures 103, 183 and 203 K (i.e. below the temperature of dielectric permittivity maximum — Tm) shown that elementary cell parameters change non-monotonically at temperatures lower then Tm (Tm≈240 K). By that Debay–Waller factors (DWFʹs) of Pb atoms are considerably greater than DWFʹs of another atoms in PMN, also it has been stated that disordered shifts of Pb atoms in x- and y-directions increase with decreasing temperature (for T<Tm).