Abstract: Using Landau-Ginzburg-Devonshire (LGD) theory for BiFeO3 dense fine-grained ceramics with quasispherical grains and nanosized intergrain spaces enriched by elastic defects, we calculated a surprisingly strong size-induced increase in the antiferromagnetic transition temperature caused by the joint action of rotomagnetic and magnetostrictive coupling. Notably, all parameters included in the LGD functional have been extracted from experiments, not assumed. Complementarily, we performed experiments for dense BiFeO3 ceramics, which revealed that the shift of the antiferromagnetic transition is to TN ∼ 690 K instead of TN ∼ 645 K for a single crystal. To explain the result theoretically, we consider the possibility of controlling the antiferromagnetic state of multiferroic BiFeO3 via biquadratic antiferrodistortive rotomagnetic, rotoelectric, magnetoelectric, and magnetostrictive couplings. According to our calculations, the highest contribution is the rotostriction contribution, while the magnetostrictive and electrostriction contributions appear smaller.
Title: Rotomagnetic coupling in fine-grained multiferroic BiFeO3: Theory and experiment
Authors: Anna N. Morozovska, Eugene A. Eliseev, Maya D. Glinchuk, Olena M. Fesenko, Vladimir V. Shvartsman, Venkatraman Gopalan, Maxim V. Silibin, and Dmitry V. Karpinsky
DOI: https://doi.org/10.1103/PhysRevB.97.134115 Physical Review B () 97, 134115
Preprint deposited in the repository: https://arxiv.org/abs/1803.02805