Eur. Phys. J. B 14, 477-481 (2000)
https://doi.org/10.1007/s100510051056

Ferroelectricity and structure of BaTiO₃ grown on YBa₂Cu₃O_7-δ thin films

Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany

Received: 24 June 1999
Revised: 27 August 1999
Published online: 15 April 2000

Abstract

We have investigated the crystal structure and the ferroelectric properties of BaTiO₃ thin films with YBa₂Cu₃O_7-δ as the bottom and Au as the top electrode. Epitaxial heterostructures of YBa₂Cu₃O_7-δ and BaTiO₃ were prepared by dc and rf sputtering, respectively. The crystal structure of the films was characterised by X-ray diffraction. The ferroelectric behaviour of the BaTiO₃ films was confirmed by hysteresis loop measurements using a Sawyer Tower circuit. We obtain a coercive field of 30 kV/cm and a remanent polarisation of 1.25 μC/cm². At sub-switching fields the capacitance of the films obeys a relation analogous to the Rayleigh law. This behaviour indicates an interaction of domain walls with randomly distributed pinning centres. At a field of 5 MV/m we calculate a 3% contribution of the irreversible domain wall motion to the total dielectric constant.