Saha, Surajit ; Ghalsasi, Pallavi ; Muthu, D. V. S. ; Singh, Surjeet ; Suryanarayanan, R. ; Revcolevschi, A. ; Sood, A. K. (2012) Phonon anomalies and structural transition in spin-ice Dy2Ti2O7: a simultaneous pressure - and temperature-dependent Raman study Journal of Raman Spectroscopy . No pp. given. ISSN 0377-0486
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Official URL: http://iisc.academia.edu/SurajitSaha/Papers/117901...
Abstract
We revisit the assignment of Raman phonons of rare-earth titanates by performing Raman measurements on single crystals of O18-isotope rich spin-ice Dy2Ti2O718 and non-magnetic Lu2Ti2O718 pyrochlores and compare the results with their O16 counterparts. We show that the low wavenumber Raman modes below 250 cm#8722;1 are not due to oxygen vibrations. A mode near 200 cm#8722;1, commonly assigned as F2g phonon which shows highly anomalous temperature dependence, is now assigned to a disorder induced Raman active mode involving Ti4+ vibrations. Moreover, we address here the origin of the "new" Raman mode, observed earlier below Tc ~ 110 K in Dy2Ti2O7, through a simultaneous pressure- and temperature-dependent Raman study. Our study confirms the "new" mode to be a phonon mode. We find that dTc/dP = + 5.9 K/GPa. Temperature dependence of other phonons has also been studied at various pressures up to ~8 GPa. We find that pressure suppresses the anomalous temperature dependence. The role of the inherent vacant sites present in the pyrochlore structure in the anomalous temperature dependence is also discussed.
Item Type: | Article |
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Source: | Copyright of this article belongs to John Wiley and Sons. |
ID Code: | 79907 |
Deposited On: | 30 Jan 2012 05:06 |
Last Modified: | 30 Jan 2012 05:06 |
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