Tunable Magnetoresistive Gas Sensing Enabled by La-Deficient LaFeO₃

Resistive sensors are widely used to detect gases, but integrating magnetoresistive effects for enhanced selectivity and sensitivity remains largely unexplored. Here we have investigated several magnetic materials in a metal oxide semiconductor (MOS) sensor, showing that iron oxides can exhibit both positive and negative magnetoresponses at relatively low operating temperatures (120-160 °C), with no simple correlation between magnetoresponse and bulk magnetization, leading to the discovery of La_0.8FeO₃ as an outstanding material for magnetoresistive gas sensing. Under a 0.9 T magnetic field, La_0.8FeO₃ shows a 134% increase in response to 40 ppm of NO₂ in air. The paramagnetism of oxygen gas is found to provide a substantial magnetosensing contribution, as the use of nitrogen as the background gas diminishes the magnetoresponse of La_0.8FeO₃ by a factor of 3. Our findings establish magnetic field modulation as a powerful strategy for tuning gas sensor performance, opening new directions in sensing technologies.