Temperature Dependence of Magnon-Phonon Sidebands in KMnF3

Temperature dependence of the fine structure in the optical-absorption spectrum is measured on the ${}_{}{}^6{}_{}{}^{}A_1^{}{}_{}{}^{}\to [{}_{}{}^4{}_{}{}^{}E,{}_{}{}^4{}_{}{}^{}A_1^{}{}_{}{}^{}]$ transition in KMn${\mathrm{F}}_3$. All the components are classified into an excitonic transition and magnon-phonon sidebands. Some of the sidebands have the same temperature dependence as the sublattice magnetization, while the others show weak dependence with temperature. A hot band due to the magnon-phonon absorption is also observed.