Anomalous temperature dependence of phonons and photoluminescence bands in pyrochlore Er(2)Ti(2)O(7): signatures of structural deformation at 130 K

Saha, Surajit and Prusty, Sudakshina and Singh, Surjeet and Suryanarayanan, R and Revcolevschi, A and Sood, AK (2011) Anomalous temperature dependence of phonons and photoluminescence bands in pyrochlore Er(2)Ti(2)O(7): signatures of structural deformation at 130 K. In: Journal of Physics: Condensed Matter, 23 (44).

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Abstract

We report a Raman study of single crystal pyrochlore Er(2)Ti(2)O(7) as a function of temperature from 12 to 300 K. In addition to the phonons, various photoluminescence (PL) lines of Er(3+) in the visible range are also observed. Our Raman data show an anomalous red-shift of two phonons (one at similar to 200 cm(-1) and another at similar to 520 cm(-1)) upon cooling from room temperature which is attributed to phonon-phonon anharmonic interactions. However, the phonons at similar to 310, 330, and 690 cm(-1) initially show a blue-shift upon cooling from room temperature down to about 130 K, followed by a red-shift, indicating a structural deformation at similar to 130 K. The intensities of the PL bands associated with the transitions between the various levels of the ground state manifold ((4)I(15/2)) and the (2)H(11/2) as well as (4)S(3/2) excited state manifolds of Er(3+) show a change at similar to 130 K. Moreover, the temperature dependence of the peak position of the two PL bands shows a change in their slope (d(omega)/d(T)) at similar to 130 K, thus further strengthening the proposal of a structural deformation. The temperature dependence of the peak positions of the PL bands has been analyzed using the theory of optical dephasing in crystals.

Item Type:	Journal Article
Publication:	Journal of Physics: Condensed Matter
Publisher:	IOP Publishing ltd
Additional Information:	Copyright of this article belongs to IOP Publishing ltd.
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	05 Dec 2011 09:00
Last Modified:	05 Dec 2011 09:00
URI:	http://eprints.iisc.ac.in/id/eprint/42527

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