Enhancing Delta Effect at High Temperatures of Galfenol/Ti/Single-Crystal Diamond Resonators for Magnetic Sensing.

A conventional wisdom is that the sensing properties of magnetic sensors at high temperatures will be degraded due to the materials' deterioration. Here, the concept of high-temperature enhancing magnetic sensing is proposed based on the hybrid structure of SCD MEMS resonator functionalized with a high thermal-stable ferromagnetic galfenol (FeGa) film. The delta effect of the magnetostrictive FeGa thin film on Ti/SCD cantilevers is investigated by varying the operating temperature from 300 to 773 K upon external magnetic fields. The multilayer structure magnetic sensor presents a high sensitivity of 71.1 Hz/mT and a low noise level of 10 nT/√Hz at 773 K for frequencies higher than 7.5 kHz. The high-temperature magnetic sensing performance exceeds those of the reported magnetic sensors. Furthermore, an anomalous behavior is observed on the delta effect, which exhibits a positive temperature dependence with the law of . Based on the resonance frequency shift of the FeGa/Ti/SCD cantilever, the strain coupling in the multilayers of the FeGa/Ti/SCD structure under a magnetic field is strengthened with increasing temperature. The delta effect shows a strong relationship with the azimuthal angle, θ, as a sine function at 300 and 773 K. This work provides a strategy to develop magnetic sensors for high-temperature applications with performance superior to that of the present ones.