Spin-driven ferroelectricity phenomena have drawn great interest in the scientific community due to potential application in spintronics and their complex physical mechanisms. A noticeable example of this is multiferroic $\mathrm{BaYFe}{\mathrm{O}}_4$ that exhibits an unconventional magnetoelectric (ME) coupling due to the uncorrelated behavior of the ferroelectric and cycloidal states under an applied magnetic field. To shed more light on this spin-driven ME effect, a high-quality sample of $\mathrm{BaYFe}{\mathrm{O}}_4$ was synthesized by a standard solid-state reaction method, and its high-field (up to 9 T) magnetic properties have been systematically investigated by means of magnetometry, magnetocaloric effect, and Mössbauer measurements over a wide temperature range (5–400 K). In addition, its crystal and magnetic structures have been studied using x-ray and neutron powder diffraction. Results obtained indicate that Fe spins form a long-range spin density wave (SDW) antiferromagnetic (AFM) order at $T_{\mathrm{N}1}\sim 50\mathrm{K}$, which transforms into the cycloidal AFM order at $T_{\mathrm{N}2}\sim 35\mathrm{K}$. A spin-glass-like state emerges below $T^{*}\sim 17\mathrm{K}$, and coexists with the long-range cycloidal AFM one in this temperature range. Magnetocaloric and Mössbauer measurements consistently confirm the robustness of both the long-range SDW and cycloidal AFM orders under applied magnetic fields up to 6 T, whereas the spin-glass state is converted into the ferromagnetic (FM) state when the applied magnetic field exceeds 1 T. These findings pinpoint the fact that the magnetic field evolution of spin correlations from the AFM to FM character in the spin-glass state is responsible for the magnetic field dependence of ferroelectricity in $\mathrm{BaYFe}{\mathrm{O}}_4$.

• Received 24 December 2020
• Revised 19 March 2021
• Accepted 30 March 2021
• Corrected 17 August 2023

DOI:https://doi.org/10.1103/PhysRevMaterials.5.044407