Eur. Phys. J. B 78, 417-428 (2010)
https://doi.org/10.1140/epjb/e2010-10583-0

Ferroelectric-ferromagnetic correlations in BiMnO₃ perovskite within Landau theory: comparison with experiment

¹ Marian Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Kraków, Poland
² Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, 30-059 Kraków, Poland

Corresponding authors: ^a olga.howczak@uj.edu.pl - ^b ufspalek@if.uj.edu.pl

Received: 28 July 2010
Published online: 6 December 2010

Abstract

Here we present a simple model formulated in the spirit of Landau theory in order to qualitatively describe magnetoelectric multiferroics. The system consists of two coupled single-component order parameters P and M which represent ferroelectric and ferromagnetic phases, respectively. We show that the magnetoelectric coupling strongly renormalizes the original magnetic transition temperature, T_M T_RM (with T_RM ≫ T_M), as well as generates an additional anomaly in ferroelectric subsystem at T_RM. Under the influence of both magnetic and electric fields the concept of Arrot plot is reproduced by the Arrot planes. We compare obtained results with available experimental data for the BiMnO₃ which undergoes ferroelectric transition below 700 K (T_f) and ferromagnetic transition at 100 K (T_RM). The results are in good overall agreement with experimental data for the ferroelectromagnetic BiMnO₃. We also estimate the contribution of Gaussian fluctuations of both order parameters, that lead to corrections to the mean-field specific heat. Those corrections are still insufficient even though other quantities agree quite well with experiment. We calculate the temperature dependence of the coherence length for both types of order as well.