We report observation of surface-defect-induced room-temperature multiferroicity—surface ferromagnetism ($M_S$ at 50 kOe $\approx 0.005$ emu/g), ferroelectricity ($P_R\approx 2\mathrm{nC}/{\mathrm{cm}}^2$), and significantly large magnetoelectric coupling (decrease in $P_R$ by $\approx 80\%$ under $\approx 15$ kOe field)—in nanorods (diameter $\approx 100$ nm) of double perovskite ${\mathrm{Y}}_2{\mathrm{NiMnO}}_6$ compound. In bulk form, this system exhibits multiferroicity only below its magnetic transition temperature $T_N\approx$ 70 K. On the other hand, the oxygen vacancies, formed at the surface region (thickness $\approx 10$ nm) of the nanorods, yield long-range magnetic order as well as ferroelectricity via Dzyloshinskii-Moriya exchange coupling interactions with strong Rashba spin-orbit coupling. Sharp drop in $P_R$ under magnetic field indicates strong cross coupling between magnetism and ferroelectricity as well. Observation of room-temperature magnetoelectric coupling in nanoscale for a compound which, in bulk form, exhibits multiferroicity only below 70 K underscores an alternative pathway for inducing magnetoelectric multiferroicity via surface defects and, thus, in line with magnetoelectric property observed, for example, in domain walls or boundaries or interfaces of heteroepitaxially grown thin films which do not exhibit such features in their bulk.

• Received 15 February 2022
• Accepted 31 May 2022

DOI:https://doi.org/10.1103/PhysRevB.105.235429