Negative magnetic circular polarization of the A-band emission in KI:Sn2+

Magnetic circular polarization of the emission produced by A-band excitation in KI:Sn²⁺ has been obtained. At low temperatures, when the field is applied along 〈001〉, the emission shows a net negative circular polarization; however, when the field is along 〈111〉, the emission shows the usual positive circular polarization. The unexpected negative polarization can be explained qualitatively by the effect of a charge-compensating vacancy located in the nearest neighbor position.