Study of the local structure of Jahn-Teller distorted CuX42- (X = Cl, Br) systems by polarized charge transfer spectroscopy: Influence of chemical pressure along A(2)MX(4) (M = Mn, Zn, Cd, Hg)

The aim of this work is to investigate the Charge Transfer (CT) spectra of CuCl42- and CuBr42- complexes formed In Cu2+-doped A(2)MX(4) crystals and t heir dependence with chemical pressure when Cu2+ replaces the divalent cati on at the MCl42- tetrahedral site. A salient feature of this study is the w eak sensitivity exhibited by the CT bands to structural changes of the comp lex. A similar phenomenon has also been observed for pure chlorocuprates. T he analysis carried out on the available family of chlorocuprates indicates that the CT band-shift induced by structural distortions in CuCl42- is sma ller than that of the corresponding Crystal Field (CF) bands. We present a perturbative model for explaining the weak sensitivity of the CT bands in c omparison to the CF ones. The estimates of the model accounts for the spect roscopic results observed along the A(2)MCl(4):Cu2+ series.