Phase Transitions in Ferroelectric Thin Films and Superlattices: Thermophysical Approach

• Published in: Ferroelectrics Vol. 370; no. 1; pp. 57 - 64
• Main Authors: Strukov, B., Davitadze, S., Lemanov, V., Shulman, S., Uesu, Y., Asanuma, S., Schlom, D., Soukiassian, A.
• Format: Journal Article
• Language: English; Japanese
• Published: Taylor & Francis Group 21.10.2008; Informa UK Limited
• Subjects: ferroelectric phase transition; ferroelectric superlattices; Ferroelectric thin films; specific heat; spontaneous polarization
• ISSN: 0015-0193; 1563-5112
• DOI: 10.1080/00150190802384344

It is shown that the information about thermophysical parameters of the nanostructured ferroelectrics is a useful supplement to the traditional x-ray and dielectric data. The results of the study of the temperature dependence of heat capacity of BaTiO 3 /MgO epitaxial thin films by dynamical 3ω method for the thickness range 50-450 nm are presented. The blurred specific heat anomalies corresponding to the phase transitions were observed, and the temperature of the transitions increases with decreasing of film thickness compared with T c in a bulk sample. The causes of the severe smearing of specific heat anomalies as well as pronounced nonlinearity of the dependence of the transition temperature on the film thickness are discussed. Specific heat data for ferroelectric superlattices (BaTiO 3 ) n /(Sr TiO 3 ) m /Sr TiO 3 were obtained for the first time for the films with the average thicknesses near 100 nm.