Multifunctional Sensor Based on a Hybrid Ferromagnetic/Sol–Gel TiO2 Coating Nanostructure

Development of a multifunction sensor for detection of environmental parameters such as temperature and relative humidity is described in this work. The multifunctional sensor is based on the combination in the same sensor unit of a magnetoinductive temperature sensor (soft magnetic FeCrSiBCuNb nanocrystalline wire) and a capacitive ceramic element (TiO₂ microscale coating) for humidity detection. The sensing principle is based on the changes of electrical impedance of both the inner ferromagnetic wire (self-inductance, L) and the ceramic TiO₂ coating (capacitance, C). In the magnetoinductive temperature element, the sensor span can be suitably selected through control of the Curie temperature of the residual amorphous phase (i.e., Cr content of the residual amorphous phase). With respect to the TiO₂ coating, its doping with alkali elements (K) improves the humidity sensor sensibility. The designed cylindrical metal/TiO₂/metal capacitive structures display resistive switching phenomena (memresistive behavior) that can be employed in design of simplified signal conditioning switches.