Polar phonon mixing in magnetoelectric EuTiO.sub.3./sub..

0331481 - FZÚ 2010 RIV DE eng J - Journal Article
Goian, Veronica - Kamba, Stanislav - Hlinka, Jiří - Vaněk, Přemysl - Belik, A.A. - Kolodiazhnyi, T. - Petzelt, Jan
Polar phonon mixing in magnetoelectric EuTiO₃.
[Míchání polárních fononů v magnetoelektrickém EuTiO₃.]
European Physical Journal B. Roč. 71, č. 3 (2009), 429-433. ISSN 1434-6028. E-ISSN 1434-6036
R&D Projects: GA ČR(CZ) GA202/09/0682
Institutional research plan: CEZ:AV0Z10100520
Keywords : multiferroics * infrared spectroscopy * phonons
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 1.466, year: 2009

Infrared reflectivity spectra of antiferromagnetic incipient ferroelectric EuTiO3 were investigated up to 600 K. Analysis of phonon plasma frequencies showed that the lowest-energy TO1 phonon correspond predominantly to the Slater mode describing vibration of Ti cations against the oxygen octahedra. TO2 phonon expresses vibrations of Eu cation against the TiO6 octahedra and the highest frequency phonon represents O-octahedra bending. Incipient ferroelectric behavior of the permittivity is caused by pronounced softening of the TO1 phonon, which is coupled to the TO2 mode. Although the Eu cations are not involved in the TO1 mode, the spin ordering of the 4f electrons at Eu cations has influence on the frequency of TO1 mode due to its coupling with TO2 mode as the consequence of superexchange interaction. This is probably responsible for 7% change of the permittivity induced by magnetic field in antiferromagnetic phase, as rep. by Katsufuji and Takagi (Phys. Rev. B 64, 054415 (2001)).

Infračervená reflexní spektra antiferomagnetického incipientního feroelektrika EuTiO3 byla studována do 600 K. Analýza fononových plazmových frekvencí prokázala, že měkký TO1 mód je spůsoben vibrací Ti proti kyslíkovým oktaedrům, zatímco TO2 mód vyjadřuje vibrace Eu proti TiO6 oktaedrům. Oba módy jsou vzájemně vázané. Ačkoli Eu vibrace naní obsažena v TO1 módu, uspořádání spinů v Eu ovlivňuje TO1 vibraci díky supervýměnné interakci mezi Eu-O-Eu.
Permanent Link: http://hdl.handle.net/11104/0176981