Infrared reflectivity of Tl1.94Mn2O6.96

We report temperature dependent infrared reflectivity of Tl1.94Mn2O6.96 in the 30 to 10 000 cm(-1) frequency range. We found that between room tempera ture and the Curie temperature (T-C congruent to T-IM) in which the insulat or-ferromagnetic metal phase transition takes place, Tl1.94Mn2O6.96 behaves as an insulator with antiresonances near the longitudinal optical modes in dicating distinctive electron-phonon interactions. Below T-C the band envel ope assigned to breathing oxygen phonons undergoes broadening and frequency hardening and the sample becomes a poor metal oxide in which small trapped polaron electrons are released with decreasing temperature. We support thi s conclusion pointing to the agreement between the experimental and the cal culated; using Reik's small polaron theory, optical conductivity strongly s uggests that conductivity be achieved by phonon assisted electron hopping. [S0163-1829(99)06833-2].