Fizika Nizkikh Temperatur: Volume 43, Number 11 (November 2017), p. 1600-1608    ( to contents , go back )

Return low-temperature phase transition in the “orbital nematic”

M.P. Kolodyazhnaya, K.R. Zhekov, I.V. Bilych, G.A. Zvyagina, and A.A. Zvyagin

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: zvyagina@ilt.kharkov.ua

Received May 10, 2017

Abstract

The influence of the external magnetic field on the Jahn–Teller phase transition at Тc ≈ 14 К is studied in the single crystal KDy(MoO4)2. At temperatures below Тc the essential change of the velocity and attenuation of acoustic modes of the crystal is discovered in the magnetic field, oriented along the [110] direction. Such a behavior of elastic characteristics is determined by the destruction of the antiferrodistorsive ordering, connected, in turn, with the ordering of the quadrupole orbital moments, charecteristic for the “orbital nematic”. The low temperature part of the H–T phase diagram for this direction of the field is restored. It is discovered that the critical temperature dependence on the field is nonmonotonic, i.e., the phase transition has the re-entrant character. Theoretical description of the observed anomalies of the temperature and magnetic field behavior of the acoustic characteristics is given.

PACS: 62.65.+k Acoustical properties of solids;
PACS: 63.20.–e Phonons in crystal lattices;
PACS: 71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn–Teller effect.

Key words: magneto-acoustic phenomena, cooperative Jahn–Teller effect, “orbital nematic”, reversible phase transition.

Published online: September 25, 2017

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