Reflectivity, transmission, and photoinduced infrared spectra of NdNiO{sub 3}
- Laboratorio Nacional de Investigacion y Servicios en Espectroscopia Optica, Centro CEQUINOR, Departamento de Quimica and Departamento de Fisica, Universidad Nacional de La Plata, Casilla de Correo 962, 1900 La Plata (Argentina)
- Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, E-28049 Madrid (Spain)
We report temperature-dependent infrared spectra of NdNiO{sub 3} prepared by synthesis under high oxygen pressure. Its room-temperature reflectivity is characteristic of a metal oxide with a Drude tail asymptotically extending to higher frequencies. The sharp metal-insulator transition is detected at about 200 K as phonons become unscreened. While their activity is in the frequency range for a distorted perovskite, the strength of involving the Nd ion against the NiO{sub 6} octahedra at 183cm{sup {minus}1} is remarkable. This and all phonon groups show strong antiresonances near the longitudinal optical frequencies and these are unusually close to absorptions seen in transmission measurements. We interpret this as evidence of strong electron-phonon interactions with carrier localization in a temperature-dependent regime. Low-temperature photoinduced spectra, excited with argon laser lines, support this picture by showing weak absorptions at about those frequencies as well as a relatively very strong photoinduced band at 810cm{sup {minus}1} and one very broad and weak peak at {approximately}2300cm{sup {minus}1} and tail up to 4000cm{sup {minus}1}. They are assigned to electronic transitions involving localized defects. Our measurements suggest that the metal-insulator phase transition in NdNiO{sub 3} is triggered by electron localization in a polaronic environment. We conclude that a suitable order parameter for perovskites with a metal-insulator phase transition may be identified in the coupling between those electrons and local spins {copyright} {ital 1997} {ital The American Physical Society}
- OSTI ID:
- 526983
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 56, Issue 3; Other Information: PBD: Jul 1997
- Country of Publication:
- United States
- Language:
- English
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