Abstract

EuTiO3 is a cubic perovskite magnetoelectric combining spin and charge degrees of freedom. The system has been shown to be a simultaneous low temperature antiferromagnet [1] and a soft mode type incipient ferroelectric [2]. A magnetoelectric coupling is present as evidenced by a strong enhancement of the dielectric constant with an applied magnetic field [3]. We report the discovery of a novel cubic to tetragonal structural phase transition and associate it with a soft phonon at the corner of the cubic Brillouin zone. We provide a comparison with the 105K transition in SrTiO3 and discuss the possible transition mechanisms accounting for the approximately 100K difference in Ts present in these systems. We further argue that EuTiO3 is an ideal system in which to study quantum critical fluctuations of coupled charge and spin order parameters by tuning the transition temperature to absolute zero resulting in multiferroic quantum criticality.

References: [1] T.R. McGuire, et al., J. Appl. Phys 37, 981 (1966) and references therein. [2] S. Kamba, et al.; Eur. Phys. Lett. 80, 27002 (2007). [3] T.Katsufuji, H.Takagi, Phys. Rev. B, 64: 054415 (2001).