X-ray and optical retardation: Evidence of structural phase transitions in (K_xNa_1−x)MnF₃ perovskite-type compounds

Abstract

X-ray and optical retardation measurements were made in order to determine whether structural phase transitions occurred in some (K _x Na_1−x )MnF₃ compounds. The measurements were carried out from 4.2 K up to the decomposition temperature for KMnF₃, (K_0.8Na_0.2)MnF₃ and NaMnF₃. For the first two crystals the temperatures of the phase transitions and changes of symmetry were observed, whilst in the latter crystal no changes of symmetry were found.

Key Words:

• X-ray and optical retardation
• Perovskite-type compounds.