Magnetoelectricity in the ferrimagnetic Cu₂OSeO₃: symmetry analysis and Raman scattering study

• Main Authors: Gnezdilov, V.P., Lamonova, K.V., Pashkevich, Yu.G., Lemmens, P., Berger, H., Bussy, F., Gnatchenko, S.L.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2010
• Series: Физика низких температур
• Subjects: Магнитоэлектрические эффекты в сегнетомагнетиках
• Online Access: http://dspace.nbuv.gov.ua/handle/123456789/117179

We report Raman scattering studies and magneto/structural symmetry analysis of the many sublattices ferrimagnet Cu₂OSeO₃ with a cubic symmetry and a linear magnetoelectric effect. There is no spectroscopic evidence for structural lattice distortions below TC = 60 K, which are expected due to magnetoelectric coupling. Using symmetry arguments we explain this observation by considering a special type of ferrimagnetic ground state which does not generate a spontaneous electric polarization. Interestingly, Raman scattering shows a strong increase of electric polarization of media through a dynamic magnetoelectric effect as a remarkable enhancement of the scattering intensity below TC. New lines of purely magnetic origin have been detected in the magnetically ordered state. A part of them are attributed as scattering on exchange magnons. Using this observation and further symmetry considerations we argue for strong Dzyaloshinskii–Moriya interaction existing in the Cu₂OSeO₃.