Fizika Nizkikh Temperatur: Volume 43, Number 11 (November 2017), p. 1647-1656    ( to contents , go back )

Investigation of structural phase transition in the KDy(MoO4)2 single crystal by Raman scattering

A.V. Peschanskii

B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Nauky Ave., Kharkiv 61103, Ukraine
E-mail: peschansky@ilt.kharkov.ua

Received June 19, 2017

Abstract

Raman light scattering in the KDy(MoO4)2 was studied in the frequency region of 3–1000 cm–1 in the temperature range from 2 to 300 K including the tem-perature of structural phase transition of Jahn–Teller cooperative effect (ТС ~ 14.5 K). The appearance of a number of additional phonon lines assigned with Ag, B1g, B2g, B3g modes was found as a result of the phase transition in the low-temperature phase that is caused by unit cell doubling. On the basis of the analysis of symmetry of phonon modes it was concluded that symmetry of the low-temperature phase is preferably monoclinic with conservation of the axis of second order along the b crystallographic direction, i.e., it is perpendicular to the layers. Low-energy electronic transitions are determined between levels of main multiplet 6H15/2 of Dy3+ ion splitted by the crystal field with the symmetry C2. At low temperatures four lines (16.5, 21.0, 24.9 и 29.1 сm–1 (2 K)) were observed in range of first excited Kramers doublet of Dy3+ ion in the KDy(MoO4)2 crystal in Raman spectrum instead of one line (18.3 сm–1 (25 K)) above the phase transition temperature (14.5 K). This fact points on the presence of four nonequivalent ions of dysprosium in the low-temperature phase.

PACS: 71.70.Ch Crystal and ligands fields;
PACS: 78.30.–j Infrared and Raman spectra and scattering.

Key words: Raman spectroscopy, phase transition, phonon, low-energy electronic excitation.

Published online: September 25, 2017

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