Absorption of Light by Pairs of Exchange-Coupled Manganese and Nickel Ions in Cubic Perovskite Fluorides

Abstract

The absorption of light by exchange‐coupled pairs of manganese and nickel ions in KZnF₃ is reported. Three absorption regions are discussed, of which two (4000 and 3300 Å) are associated with electronic excitation of the manganese and the third (6600 Å) corresponds to electronic excitation of the nickel ion. The lines can be analyzed by means of an exchange interaction of the type JS·S and a value of J = 18 cm⁻¹ for the manganese—nickel pair in its electronic ground state has been obtained. The mechanism of the electronic transitions has been discussed using the theory developed for like pairs in an earlier paper and reasons for the greater intensity of absorption by unlike pairs are considered. Corresponding effects of exchange interaction have also been observed in the spectra of KMn_xNi_1−xF₃ crystals. The energies and intensities of the absorption bands have been measured as a function of x and a theoretical analysis of the main results has been given. The main features of these spectra can be interpreted satisfactorily using our model for a pair of exchange‐coupled ions.