Jahn–Teller effect under pressure

Abstract

This work deals with structural correlation studies in Jahn–Teller (JT) systems of Cu²⁺ and Mn³⁺ in the layer perovskites A₂CuCl₄ and AMnF₄. The aim is to explore the influence of the JT effect on the materials' properties as well as its variation with pressure. We present structural studies carried out in the layer perovskites AMnF₄ by optical spectroscopy under pressure in order to explore whether pressure reduces the JT distortion or induces tilting phenomena of the JT octahedra (MnF₆)³⁻. The influence of the JT effect on the stabilization of the ground-state spin, either high-spin (HS) or low-spin (LS), in Mn³⁺ is analyzed. This knowledge is important to understand and, eventually predict, magnetic, electrical and optical properties in connection with HS–LS phenomena. The results are compared with previous structural studies performed in the (CuCl₆)⁴⁻ JT octahedra formed in A₂CuCl₄.

Keywords:

• Mn³⁺
• Cu²⁺
• Jahn–Teller effect
• Spectroscopy under pressure
• Layer perovskite

Acknowledgements

The XAS experiments were done at LURE under proposal (Project PS 048-03). This work has been financed by the Spanish M.E.C. (Project Ref. MAT2005-00099).