Phonon anomalies and structural transition in spin ice Dy2Ti2O7: a simultaneous pressure-dependent and temperature-dependent Raman study

Saha, Surajit and Ghalsasi, Pallavi and Muthu, DVS and Singh, Surjeet and Suryanarayanan, R and Revcolevschi, A and Sood, AK (2012) Phonon anomalies and structural transition in spin ice Dy2Ti2O7: a simultaneous pressure-dependent and temperature-dependent Raman study. In: JOURNAL OF RAMAN SPECTROSCOPY, 43 (8). pp. 1157-1165.

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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 nonmagnetic Lu2Ti2O718 pyrochlores and compare the results with their O16 counterparts. We show that the low-wavenumber Raman modes below 250 cm-1 are not due to oxygen vibrations. A mode near 200 cm-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 below TC similar to 110 K in Dy2Ti2O7, through a simultaneous pressure-dependent 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 similar 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. Copyright (c) 2012 John Wiley & Sons, Ltd.

Item Type:	Journal Article
Publication:	JOURNAL OF RAMAN SPECTROSCOPY
Publisher:	WILEY-BLACKWELL
Additional Information:	Copy right for this article belongs to WILEY-BLACKWELL, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA
Keywords:	geometrically frustrated pyrochlore;low-temperature and high-pressure physics;Raman spectroscopy;phonon anharmonicity;crystal field transition
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	15 Oct 2012 05:07
Last Modified:	15 Oct 2012 05:07
URI:	http://eprints.iisc.ac.in/id/eprint/45095

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