The temperature dependence of Co2+‐ion absorption‐band maxima has been studied in crystals of RbCoF3, KMn0.975Co0.025F3and KNi0.75Co0.25F3. Shifts in the cobalt‐band maxima are superimposed on changes of purely thermal origin. The additional changes in the band maxima are attributed to the magnetic properties of these materials. In pure cobalt salts the magnetically induced changes begin, with decreasing temperature, at the Ne´el temperatures of the materials. Similarly, in salts where the cobalt ion is not a major constituent, the shifts in the Co2+bands appear approximately at the Ne´el temperature of the host.