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Phys. Rev. B 65, 235113 (2002) [6 pages]

Temperature-dependent Raman spectroscopy in BaRuO3 systems

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Y. S. Lee*
Center for Strongly Correlated Materials Research, Seoul National University, Seoul 151-747, Korea

T. W. Noh
School of Physics and Research Center for Oxide Electronics, Seoul National University, Seoul 151-747, Korea

J. H. Park and K.-B. Lee
Department of Physics, Pohang University of Science and Technology, Pohang, Korea

G. Cao† and J. E. Crow
National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306

M. K. Lee and C. B. Eom
Department of Material Science and Engineering, University of Wisconsin—Madison, Madison, Wisconsin 53706

E. J. Oh and In-Sang Yang‡
Department of Physics, Ewha Womans University, Seoul 120-750, Korea

Received 14 January 2002; published 10 June 2002

We investigated the temperature dependence of the Raman spectra of a nine-layer BaRuO3 single crystal and a four-layer BaRuO3 epitaxial film, which show pseudogap formations in their metallic states. From the polarized and depolarized spectra, the observed phonon modes are assigned properly according to the predictions of group theory analysis. In both compounds, with decreasing temperature, while A1g modes show a strong hardening, Eg (or E2g) modes experience a softening or no significant shift. Their different temperature-dependent behaviors could be related to a direct Ru metal bonding through the face sharing of RuO6. It is also observed that another E2g mode of the oxygen participating in the face sharing becomes split at low temperatures in the four-layer BaRuO3. And, the temperature dependence of the Raman continua between 250 and 600 cm-1 is strongly correlated to the square of the plasma frequency. Our observations imply that there should be a structural instability in the face-shared structure, which could be closely related to the pseudogap formation of BaRuO3 systems.

© 2002 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.65.235113
DOI:
10.1103/PhysRevB.65.235113
PACS:
78.30.-j, 63.20.-e, 71.45.Lr

*Email address: yslee@phya.snu.ac.kr

†Present address: Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506.

‡Corresponding author. Email address: yang@mm.ewha.ac.kr

 
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