LOCAL-STRUCTURE DETERMINATION OF MN2+ IN THE ABCL(3)MN2+ CHLOROPEROVSKITES BY EXAFS AND OPTICAL SPECTROSCOPY

This work reports the local structure around the manganese in the ABCl(3):Mn2+ (A = K, Rb, Ca and B = Mg, Ca, Cd, Sr) chloroperovskite series. EXAFS and XANES experiments carried out in KMgCl3:Mn2+ and RbCaCl3:Mn2+ indicate that the Mn-Cl distances of the MnCl64- complex are 2.51 and 2.53 Angstrom, respectively. These values are very similar to those found in the pure NH4MnCl3 perovskite, R = 2.525 Angstrom, and show that the variations of R along the series do not follow that of the host lattice. The correlation between these measurements and the optical excitation spectra allows us to estimate Mn-Cl bond distances for the whole series with accuracies of about 0.002 Angstrom. The present results are compared with previous structural data reported for the ABF(3):Mn2+ isomorphous fluorides.