Local structure of Cu2+ in the (C2H5NH3)(2)MCl4:Cu2+ (M=Cd, Mn) layer perovskites. Influence of hydrostatic pressure in the 0-60 kbar range

This paper deals with the effects of pressure on the charge-transfer spectra of CuCl64- complexes formed in Cu2+ doped (C2H5NH3)(2)MCl4 (M = Cd, Mn). A pressure-induced redshift is observed for the first charge-transfer band in both crystals. While the shift is continuous for the Mn crystal at a rate of -40 cm(-1)/kbar in the 0-60 kbar range, it experiences an abrupt jump of -1400 cm(-1) around 26 kbar for the Cd crystal. Such a discontinuous behaviour is interpreted in terms of a structural change in the CuCl64- coordination geometry from an axially elongated octahedron to a more compressed geometry. The present results are compared with those reported for the pure (C2H5NH3)(2)CuCl4 crystal.