Jahn-Teller effect under pressure

摘要

This work deals with structural correlation studies in Jahn-Teller (JT) systems of Cu~(2+) and Mn~(3+) in the layer perovskites A_(2)CuCl_(4) and AMnF_(4). 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 AMnF_(4) by optical spectroscopy under pressure in order to explore whether pressure reduces the JT distortion or induces tilting phenomena of the JT octahedra (MnF_(6))~(3-).^sThe influence of the JT effect on the stabilization of the ground-state spin, either high-spin (HS) or low-spin (LS), in Mn~(3+) 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 (CuCl_(6))~(4-)^sJT octahedra formed in A_(2)CuCl_(4).