Béa H, Dupé B, Fusil S, Mattana R, Jacquet E, Warot-Fonrose B, Wilhelm F, Rogalev A, Petit S, Cros V, Anane A, Petroff F, Bouzehouane K, Geneste G, Dkhil B, Lisenkov S, Ponomareva I, Bellaiche L, Bibes M, Barthélémy A
Unité Mixte de Physique CNRS/Thales, Campus de l'Ecole Polytechnique, 1 Av. A. Fresnel, 91767 Palaiseau, France.
Phys Rev Lett. 2009 May 29;102(21):217603. doi: 10.1103/PhysRevLett.102.217603. Epub 2009 May 27.
In the search for multiferroic materials magnetic compounds with a strongly elongated unit-cell (large axial ratio c/a) have been scrutinized intensely. However, none was hitherto proven to have a switchable polarization, an essential feature of ferroelectrics. Here, we provide evidence for the epitaxial stabilization of a monoclinic phase of BiFeO3 with a giant axial ratio (c/a=1.23) that is both ferroelectric and magnetic at room temperature. Surprisingly, and in contrast with previous theoretical predictions, the polarization does not increase dramatically with c/a. We discuss our results in terms of the competition between polar and antiferrodistortive instabilities and give perspectives for engineering multiferroic phases.
在寻找多铁性材料的过程中，具有高度拉长的晶胞（大的轴比c/a）的磁性化合物受到了深入研究。然而，迄今为止，尚未有证据表明这些化合物具有可切换的极化特性，而这是铁电体的一个基本特征。在此，我们提供证据表明，BiFeO₃单斜相具有巨大的轴比（c/a = 1.23），在室温下同时具有铁电和磁性，并且能够外延稳定。令人惊讶的是，与先前的理论预测相反，极化并不随c/a显著增加。我们根据极性和反铁电畸变不稳定性之间的竞争来讨论我们的结果，并给出了设计多铁性相的前景。
