Optical Spectra of Exchange Coupled Mn++ Ion Pairs in ZnS:MnS

Abstract

The optical spectra of several ZnS:MnS (1 to 10 mole%) mixed crystals were obtained at temperatures from 4.2° to 300°K. A concentration dependence was found which proved that certain bands were due to pairs of Mn⁺⁺ ions in nearest‐neighbor cation sites. Temperature—dependent absorption bands were found which were interpreted to give an interionic exchange integral in the ground state of —9 cm^—1 in the spin—spin Hamiltonian H = —2JS₁·S₂. This agrees with the value obtained from the analysis of the susceptibility of pure MnS. The narrow bands due to transitions to the ⁴A₁, ⁴E(G) states were shown to fit an isotropic spin—spin coupling law with J = +6 cm^—1 for each state. The inversion of sign from the ground state is not fully understood. The selection rules for the transitions do not follow those for the total spin (ΔS = 0).