Lattice dynamics in Ba.sub.0.7./sub.Sr.sub.0.3./sub.TiO.sub.3./sub.: study by THz and IR spectroscopy and ab-initio simulations

0352308 - FZÚ 2011 RIV GB eng J - Journal Article
Ostapchuk, Tetyana - Petzelt, Jan - Kužel, Petr - Savinov, Maxim - Hlinka, Jiří - Tkach, A. - Vilarinho, P. M. - Lisenkov, S. - Ponomareva, I. - Bellaiche, L.
Lattice dynamics in Ba_0.7Sr_0.3TiO₃: study by THz and IR spectroscopy and ab-initio simulations.
Phase Transitions. Roč. 83, 10-11 (2010), s. 955-965. ISSN 0141-1594. E-ISSN 1029-0338
R&D Projects: GA ČR GAP204/10/0616; GA MŠMT ME08109
Institutional research plan: CEZ:AV0Z10100520
Keywords : soft mode * central mode * complex dielectric function * time-domain terahertz spectroscopy * infrared reflectivity
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 1.006, year: 2010

We report on the experimental and theoretical study of the lattice dynamics in Ba0.7Sr0.3TiO3 in 20-900 K temperature range. Complex dielectric response in the terahertz and far infrared range was evaluated from the time-domain THz transmission spectra and infrared reflectivity by means of two damped harmonic oscillator models in classical and factorized form of the dielectric function. The anisotropic dielectric function in the ferroelectric phases was extracted using the Bruggeman model of the effective medium approximation. The fitted parameters of the temperature-dependent Slater-type vibrations (soft and central modes) were compared with those obtained from ab-initio simulations. The role of the lattice phonons and central mode in the dielectric anomaly is discussed.
Permanent Link: http://hdl.handle.net/11104/0191843