Raman and optical spectroscopic studies of small-to-large polaron crossover in the perovskite manganese oxides
- Department of Physics and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)
- Department of Material Science and Engineering and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)
- Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)
- Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306 (United States)
We present an optical reflectance and Raman-scattering study of the A{sub 1{minus}x}A{sup {prime}}{sub x}MnO{sub 3} system as a function of temperature and doping (0.2{le}x{le}0.5). The metal-semiconductor transition in the A{sub 1{minus}x}A{sup {prime}}{sub x}MnO{sub 3} system is characterized by a change from a diffusive electronic Raman-scattering response in the high-temperature paramagnetic phase, to a flat continuum scattering response in the low-temperature ferromagnetic phase. We interpret this change in the scattering response as a crossover from a small-polaron-dominated regime at high temperatures to a large-polaron-dominated low-temperature regime. Interestingly, we observe evidence for the coexistence of large and small polarons in the low-temperature ferromagnetic phase. We contrast these results with those obtained for EuB{sub 6}, which is a low-T{sub c} magnetic semiconductor with similar properties to the manganites, but with a substantially reduced carrier density and polaron energy. {copyright} {ital 1998} {ital The American Physical Society}
- OSTI ID:
- 643348
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 58, Issue 5; Other Information: PBD: Aug 1998
- Country of Publication:
- United States
- Language:
- English
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