Magnetodielectric effect and optic soft mode behaviour in quantum paraelectric EuTiO₃ ceramics

¹  Institute of Physics ASCR - v.v.i. Na Slovance 2, 182 21 Prague 8, Czech Republic
²  Arrhenius Laboratory, Stockholm University - SE-10691 Stockholm
³  Brno University of Technology - Technicka 2896/2, 616 69 Brno, Czech Republic
⁴  Grenoble High Magnetic Field Lab, CNRS - 25, avenue des Martyrs, Grenoble Cedex 9, France

Received: 20 July 2007
Accepted: 29 August 2007

Abstract

Infrared reflectivity and time-domain terahertz transmission spectra of EuTiO₃ ceramics revealed a polar optic phonon at 6-300 K whose softening is fully responsible for the recently observed quantum paraelectric behaviour. Even if our EuTiO₃ ceramics show lower permittivity than the single crystal due to a reduced density and/or small amount of secondary pyrochlore Eu₂Ti₂O₇ phase, we confirmed a magnetic field dependence of the permittivity, also slightly smaller than in single crystal. An attempt to reveal the soft phonon dependence at 1.8 K on the magnetic field up to 13 T remained below the accuracy of our infrared reflectivity experiment.