Magnetic Field-Enhanced NO ₂ Sensing in Co ₃ O ₄ Microcubes: Insights from Magnetic Structure Evolution

A magnetic field can modulate the density and transport of charge carriers through magnetic moment rearrangement and Lorentzian forces, as well as enhance oxygen adsorption on semiconductor surfaces. This dual-action mechanism provides a robust platform for engineering sensitivity in metal oxide gas sensors. In this study, antiferromagnetic mesoporous Co₃O₄ microcubes were prepared by a hydrothermal method for ultrasensitive NO₂ gas detection at room temperature under the assistance of a magnetic field. The gas response exhibits significant magnetic field enhancement to 0.5-100 ppm NO₂, showing positive correlation with both field strength (≤150.8 mT) and gas concentration. At 150.8 mT, the response to 500 ppb NO₂ increased nearly four-fold, with sensitivity increasing from 8 to 30. First-principles calculations combined with experimental studies reveal the magnetic structure evolution due to the adsorption enhancement of nitrogen dioxide/oxygen on bidentate cobalt sites under magnetic fields, establishing a physical mechanism of magnetic field-enhanced gas sensing. This work demonstrates magnetic field modulation as a generalizable strategy to transcend the performance limits of conventional metal oxide gas sensing materials.