Temperature-dependent Raman and X-ray studies of the spin-ice pyrochlore Dy2Ti2O7 and non-magnetic pyrochlore Lu2Ti2O7

Saha, Surajit ; Singh, Surjeet ; Dkhil, B. ; Dhar, S. ; Suryanarayanan, R. ; Dhalenne, G. ; Revcolevschi, A. ; Sood, A. K. (2008) Temperature-dependent Raman and X-ray studies of the spin-ice pyrochlore Dy2Ti2O7 and non-magnetic pyrochlore Lu2Ti2O7 Physical Review B: Condensed Matter and Materials Physics, 78 (21). 214102_1-214102_10. ISSN 1098-0121

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Official URL: http://prb.aps.org/abstract/PRB/v78/i21/e214102

Related URL: http://dx.doi.org/10.1103/PhysRevB.78.214102

Abstract

We present here temperature-dependent Raman, X-ray diffraction, and specific heat studies between room temperature and 12 K on single crystals of spin-ice pyrochlore compound Dy2Ti2O7 and its non-magnetic analog Lu2Ti2O7. Raman data show a "new" band not predicted by factor group analysis of Raman-active modes for the pyrochlore structure in Dy2Ti2O7 , appearing below a temperature of Tc=110 K with a concomitant contraction of the cubic unit cell volume as determined from the powder X-ray diffraction analysis. Low-temperature Raman experiments on O18-isotope substituted Dy2Ti2O7 confirm the phonon origin of the new mode. These findings, absent in Lu2Ti2O7, suggest that the room-temperature cubic lattice of the pyrochlore Dy2Ti2O7 undergoes a "subtle" structural transformation near Tc. We find anomalous redshift of some of the phonon modes in both the Dy2Ti2O7 and the Lu2Ti2O7 as the temperature decreases, which is attributed to strong phonon-phonon anharmonic interactions.

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Source:Copyright of this article belongs to American Physical Society.
ID Code:50236
Deposited On:22 Jul 2011 14:01
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