Enhanced Sensitivity of ZnFe₂O₄ Based on Ordered Magnetic Moment Induced by Magnetic Field: A New Insight into Mechanism

Abstract

Semiconductor gas sensor mainly relies on the interaction between sensitive materials and gas to obtain gas information. Deep insight into the interaction mechanism is increasingly important for designing high performance gas sensors. Here, ZnFe2O4 microspheres (MSs) are utilized with tunable magnetism through the assistance of magnetic field to study the essential elements of sensitive processes. The gas sensing properties of ZnFe2O4 MS under different applied magnetic field intensities and various gaseous environments are systematically investigated. The results suggest that ordered magnetic moment induced by magnetic field promotes the probability of contact and reaction between gases and sensitive materials, thus significantly improving the sensitivity. Especially, ZnFe2O4 annealed at 500 °C sensor under the action of 54.6 mT magnetic field exhibits excellent ethanol detection performance (S = 67.8), which is ≈4 times higher than that without magnetic field. By carefully analyzing the experimental results, this research proposes a new physical model called “port docking” to re‐explain the sensitivity mechanism. This work systematically studies the role of the magnetic moment in the sensing process, and provides a new idea for designing high‐performance gas sensors.

Magnetic Chemiresistive Fe-Doped In2O3 Nanocubes to Tunably Detect NO2 at ppm to ppb Concentrations

“…So far, enhanced sensitivity with the assistance of a magnetic field has been attributed to the interaction of aligned magnetic dipole moments within both the gas and the sensor materials. 25,26 According to the "Port Docking" model recently proposed by Zhang and coauthors, the exchange of electrons between the analyte and the sensitive materials, driven by the Lorentz force under the magnetic field, contributes to increased oxygen absorption and gas sensitivity in magnetic materials. 26 In the present study, it can be noticed from Tables 1, S1, and Figure 7 that magnetic field-driven enhancement in the NO 2 sensing responses has been found for both diamagnetic In 2 O 3 and ferromagnetic Fe-doped In 2 O 3 .…”

“…25,26 According to the "Port Docking" model recently proposed by Zhang and coauthors, the exchange of electrons between the analyte and the sensitive materials, driven by the Lorentz force under the magnetic field, contributes to increased oxygen absorption and gas sensitivity in magnetic materials. 26 In the present study, it can be noticed from Tables 1, S1, and Figure 7 that magnetic field-driven enhancement in the NO 2 sensing responses has been found for both diamagnetic In 2 O 3 and ferromagnetic Fe-doped In 2 O 3 . Despite being a diamagnetic material, the reason for the small enhancement of NO 2 sensing response in the case of In 2 O 3 is probably due to the enhancement in the quantity of surface adsorbed oxygen species due to the applied magnetic field as shown in Figure 10.…”

“…25 Very recently, another work based on magnetic field-assisted gas sensing has been reported by Zhang and co-workers. 26 field. 26 In a different kind of work, Sun and co-workers were able to modify the conductance of the Cu 2 O/NiO interface and surface oxygen adsorption using an external magnetic field.…”

“…26 field. 26 In a different kind of work, Sun and co-workers were able to modify the conductance of the Cu 2 O/NiO interface and surface oxygen adsorption using an external magnetic field. 27 As a consequence, Sun and co-workers have obtained a 61% enhancement in H 2 S sensing.…”

“…Sensing response within detection limits is, however, a property that can be optimized in various ways. The sensing performance of chemiresistors can be improved by tailoring internal parameters like chemical composition, vacancy, nanostructure, surface morphology, topological polar surface area (TPSA) of analytes, and crystal-micro-electronic structure. − On the other hand, the use of external stimuli like ultraviolet (UV)-visible light excitation and temperature is quite common to increase a sensor’s response. − Application of an external magnetic field to enhance the gas sensing response of chemiresistive materials is a recent breakthrough that can also be used for enhancing a sensor’s response. , The first case of external magnetic field-assisted paramagnetic gas sensing by chemiresistive method by a metal oxide semiconductor (MOS) has been reported by our group . In that work, the static external magnetic field generated using a permanent ferrite ring magnet was used to enhance the response of Ni 1– x V x O 1– y toward paramagnetic NO by 30% .…”