Magnetic Field Modulates Butterfly-Hysteretic Formaldehyde Response in Sm-Doped BiFeO₃ Sensors

The development of a high-performance formaldehyde gas sensor is essential for protecting human health and monitoring environmental quality. Beyond conventional chemical modification strategies, the inherent magnetoelectric coupling effect of multiferroic materials offers another promising approach, even though magnetic fields have not conventionally been considered as direct triggers for the sensing processes. In this study, we demonstrate that gas sensors fabricated with 5% samarium (Sm)-doped BiFeO₃ exhibit a distinctive butterfly-hysteretic magnetic field-dependent response behavior toward formaldehyde. Under an external magnetic field of 100 mT, the detection limit decreased from 90 to 50 ppb, the overall response kinetics accelerated by 207%, and the gas response to 20 ppm formaldehyde increased by 161%. These enhancements are attributed to magnetic field-generated surface polarization and domain wall motion resulting from the intrinsic magnetoelectric effect. This work provides valuable insights into the fabrication of high-performance gas sensors and expands the application potential of multiferroics and magnetoelectric materials.