High resolution phosphorescence excitation spectroscopy of exchange coupled Mn²⁺ pairs in KMgF₃ and KZnF₃

Abstract

A study of the absorption of light by pairs of exchange coupled manganese ions in the perovskite fluorides KMgF₃ and KZnF₃ has been made using the technique of high resolution phosphorescence excitation spectroscopy. Transitions to the following pair states have been observed: ⁶ A _1g ⁴ T _1g ^a ; ⁶ A _1g ⁴ E _g ^a ; ⁶ A _1g ⁴ A _1g ; ⁶ A _1g ⁴ E _g ^b ; ⁴ T _1g ^{a 4} T _1g ^a ; ⁴ E _g ^{a 4} T _1g ^a and ⁴ A _1g ⁴ T _1g ^a . Quantitative estimates of intensities have been made for some of these transitions as well as estimates of the effective exchange parameters. A detailed analysis of the transition ⁶ A _1g ⁶ A _1g → ⁶ A _1g ⁴ A _1g provides confirmation of the Tanabe mechanism of exchange induced absorption of light by pairs of transition metal ions. It is shown that absence of MCD in this pair absorption is predicted by the Tanabe mechanism.