Local Transition of MnO₄^{2 −} Molecular Impurity Ion in Proper Ferroelastic K₃Na(CrO₄)₂

Abstract

Temperature dependences of EPR spectrum for Mn ⁶⁺ paramagnetic center embodied in MnO ₄ ^{2 −} molecular impurity ion in proper ferroelastric K ₃ Na(CrO ₄ ) ₂ were studied. Local transition due to local electron-lattice instability appearing at low temperature region T ≤ 18 K has been detected and identified for this system in the first time. Model of the phenomenon is based on the transformation of Jahn-Teller effect to pseudo-Jahn-Teller effect with its the following complete suppressing under the action of ferroelastic order parameter increase at low temperatures.

Keywords:

• ferroelastics
• molecular impurity ion
• Jahn-Teller effect
• local transition
• EPR
• K₃Na(CrO₄)₂

PACS numbers::

• 77.80.-e
• 76.30.Fc

Acknowledgments

We are grateful to A.A. Kaplyanskii for his interest in this work, and to P.G. Baranov for helpful discussions. This study was supported in part by the Russian Foundation for Basic Research, projects 05-02-17766, 04-02-17633 and 06-02-17320.