A. Pashkin — Page 2

arXiv2004

Temperature dependence of microwave and THz dielectric response in Srn+1TinO3n+1 (n=1-4)

The microwave, near-millimetre and infrared (IR) dielectric response of Srn+1TinO3n+1 (n=1-4) Ruddlesden-Popper homologous series was studied in the temperature range 10 to 300 K. Remarkable softening of the polar optical mode was observed in Sr4Ti3O10 and Sr5Ti4O13 which explains the increase in microwave permittivity and dielectric loss upon cooling. However, both samples have a distinct content of SrTiO3 dispersed between SrO layers. It is proposed therefore that the observed soft mode originates from the SrTiO3 microscopic inclusions.

cond-mat.mtrl-sci↗

arXiv2003

Comment on "Dielectric behavior of paraelectric KTaO3, CaTiO3, and (Ln_{1/2}Na_{1/2})TiO3 under a dc electric field"

Chen Ang, Bhalla and Cross [Phys. Rev. B 64, 184104 (2001)] have studied the low-frequency (20 Hz -- 100 kHz) dielectric dispersion of the KTaO3 crystal under a dc electric field. Performing fits of the electric field dependence they came to conclusion that an appreciable contribution to the dielectric permittivity originates from polar clusters. In this Comment we show that the dielectric permittivity at low frequencies (100 Hz -- 1 MHz) equals to that in the THz region, close below the polar phonon response. This excludes the possibility of any appreciable dielectric dispersion due to polar clusters. In addition, we demonstrate that correct treatment using Landau-Ginzburg-Devonshire theory allows to fit the electric field dependence of the dielectric constant without assuming any polarization mechanism besides the polar phonon modes.

cond-mat↗