γ-BaFe2O4: a fresh playground for room temperature multiferroicity

Multiferroics, showing the coexistence of two or more ferroic orderings at room temperature, could harness a revolution in multifunctional devices. However, most of the multiferroic compounds known to date are not magnetically and electrically ordered at ambient conditions, so the discovery of new materials is pivotal to allow the development of the field. In this work, we show that BaFe2O4 is a previously unrecognized room temperature multiferroic. X-ray and neutron diffraction allowed to reveal the polar crystal structure of the compound as well as its antiferromagnetic behavior, confirmed by bulk magnetometry characterizations. Piezo force microscopy and electrical measurements show the polarization to be switchable by the application of an external field, while symmetry analysis and calculations based on density functional theory reveal the improper nature of the ferroelectric component. Considering the present findings, we propose BaFe2O4 as a Bi- and Pb-free model for the search of new advanced multiferroic materials. The application of multiferroics is often limited by low ordering temperatures. Here, the authors show that BaFe2O(4) is a room temperature antiferromagnet with improper ferroelectricity, suggesting it as a playground for the study of multiferroicity.

Automated summary

This study reports a previously unrecognized room temperature multiferroic material, BaFe2O4. Experimental results demonstrate its polar crystal structure and antiferromagnetic behavior, and the polarization is switchable as observed through piezo force microscopy and electrical measurements. The findings are of great significance for the discovery and application of new multiferroic materials.