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Thickness dependence of the dielectric function of ferroelectric thin films
Author(s) -
Wesselinowa J. M.,
Trimper S.
Publication year - 2004
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200301988
Subject(s) - dielectric , materials science , condensed matter physics , thin film , transverse plane , ferroelectricity , function (biology) , dielectric loss , dielectric function , field (mathematics) , composite material , physics , nanotechnology , optoelectronics , mathematics , structural engineering , evolutionary biology , pure mathematics , engineering , biology
A Green's function technique for a modified Ising model in a transverse field is applied, which allows to calculate the real and the imaginary parts of the dielectric function ϵ ( k , E ) for ferroelectric thin films. Compared to bulk materials the frequency of the soft‐mode in thin film is reduced whereas the damping is enhanced. The dependence of ϵ ( k , E ) on temperature and film thickness is obtained for k = 0 numerically. It is demonstrated, that the maximum of the dielectric function decreases with decreasing film thickness. The temperature, where the dielectric function offers a maximum, can decrease or increase depending on the strength of the surface transverse field and the exchange interaction parameter. Due to stronger damping effects in thin films the peak in the dielectric function becomes more diffuse when the film thickness decreases. The results are in reasonable qualitative agreement with experimental data for different ferroelctrics. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)