Magnetic field sensors using VO₂/Fe₃O₄nanoparticle devices

We combined the metal-insulator transition (MIT) properties of VO₂and the magnetic properties of Fe₃O₄to realize a magnetometer with very large nonlinearity and switching characteristics. VO₂, Fe₃O₄nanoparticles, and a conductive binder (silver paint) were mixed and drop-casted onto two-terminal gap junction devices. The device's current-voltage characteristics exhibited current-switching behavior related to MIT in VO₂which changed with the external magnetic field. The magnetoresistance and magnetostriction in Fe₃O₄both contributed to the field sensitivity of the sensor. Sensitivities as high as 1 A nT^-1(or 50.8 V T^-1with a current bias) were observed near the MIT voltage. The resulting minimum detectable signal was 20 pT/SQRT(Hz).