Münster 1999 – scientific programme

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DF: Dielektrische Festkörper

DF 6: Poster

DF 6.11: Poster

Thursday, March 25, 1999, 09:30–12:30, Aula

IR-absorption of Jahn-Teller hole polarons in LaMnO₃ — •M. Wierschem¹, S. Kapphan¹, M. Gao¹, V. Vikhnin², B. Melekh², and E. Shadrin² — ¹FB Physik, University of Osnabrück, Barbarastraße 7, D-49069 Osnabrück, Germany — ²Ioffe Institute, 194 021 St. Petersburg, Russia

A IR-absorption study in LaMnO₃ crystals is performed with the aim to investigate the characteristic absorption of Jahn-Teller hole polarons (Mn⁴⁺ ions in the surrounding of Mn³⁺ Jahn-Teller ions of the host lattice). The IR-absorption and its temperature dependence is investigated with the help of a Fourier IR spektrometer (Bruker IFS 120 HR). Four well pronounced FIR absorption lines (for RT at 0.161 eV, 0.147 eV, 0.130 eV and 0.117 eV) were observed. A model of a Mn⁴⁺-centered cluster of Jahn-Teller Mn³⁺ ions in LaMnO₃ crystals and related systems, which take part in colossal magnetoresistance effects (CMR) was developed. Such Jahn-Teller hole polarons can act as the main carriers in the CMR-effect. It is suggested that the multi-well off-center structure of Mn³⁺-Jahn-Teller ions of the second coordinationsphere of the Mn⁴⁺ hole polarons can be responsible for the multipeak structure of the IR-absorption, explaining the four absorption peaks detected in the FIR.

This work is supported by DFG (SFB 225/C7) and one of us, V. Vikhnin, acknowledges support of DFG (436RUS17/112/98).