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Studies of phase transitions in Fe containing ternary perovskite multiferroics

Seminar
Tuesday, 07.05.2013 10:00 to 11:00

Speakers: Igor P. Raevski (Southern Federal University, Rostov-on-Don, Russia)
Place: Přednáškový sál, Fyzikální ústav Na Slovance
Presented in English
Organisers: Department of Dielectrics

One of the promising ways of designing new single-phase multiferroic materials is adjusting the temperatures of both ferroelectric and magnetic phase transitions by ion substitutions in the host compound to obtain the maximal magnetoelectric coupling. The aim of the present talk is a brief review of the recent studies of both ferroelectric and magnetic phase transitions in some Fe containing ternary perovskite multiferroics, especially PbFe0.5B0.5O3 (B-Nb, Ta, Sb) and related solid solutions. Possible ways to control the temperature TN of their antiferromagnetic phase transition are discussed. In our studies, besides the usual methods, we used the temperature evolution of 57Fe Mössbauer spectrum as a sensitive method of TN detection.

It is believed that in all perovskite ABO3 multiferroics, magnetic and ferroelectric subsystems are independent. Magnetic properties are provided by B-site (e.g. Mn3+ and Fe3+) cations while ferroelectric properties are provided by the A-site cations having the so-called dangling bonds (Bi3+ and Pb2+). In contrast to this assumption, also A-site ion substitutions have been found to effect greatly the TN value of PbFe0.5B0.5O3. The results obtained are discussed using the models of magnetic superexchange involving Pb2+ cations and next-nearest Fe3+ neighbours.