IR Absorption of Trapped and Free Jahn–Teller Polarons in 3D-Crystals and Films of LaMnO3 and La2/3Sr1/3MnO3

Author： WIERSCHEM M. KAPPHAN S. VIKHNIN V.

ISSN： 0015-0193

Source： Ferroelectrics, Vol.299, Iss.1, 2004-01, pp. : 49-54

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Abstract

The experimental and theoretical study of IR-absorption in LaMnO3(LMO) single crystals has led to the observation of new five well-defined peaks. Their positions at RT are the following: 0.161 eV, 0.147 eV, 0.130 eV, 0.117 eV, and a much more broadened peak at∼⃒0.24 eV. The IR-absorption and its temperature and heat treatment dependence was studied with the help of a Fourier IR spectrometer Bruker IFS 120 HR. Analogous peaks of IR-absorption in LMO films are shifted to the lower energy side. The La2/3Sr1/3MnO3film IR-absorption is characterized by additional broadening. The results were interpreted as direct detection of Jahn–Teller hole free polarons, as well as trapped hole and electronic polarons in LMO and related systems. Two type of Jahn–Teller hole states were used in this model. There were free Jahn–Teller hole polarons, and Jahn–Teller hole polarons within localized charge transfer vibronic excitons (Mn4+—Mn2+pairs). IR-absorption peak induced by electronic polaron within such type exciton mentioned above was also interpreted.