Micromagnetic Sensor Utilizing Single SAW IDT Shunt-Loaded with GMI Wire

A miniaturized magnetic sensor design utilizing a GMI microwire and a single SAW IDT is presented. One possible application for this sensor design is to detect the small changes in magnetic susceptibility in lithium-ion batteries associated with changes in the internal state of the battery. This design is selected to take advantage of the coupling of the impedance characteristics of the GMI microwire to the IDT transduction process. As a result, high sensitivity in the low magnetic field ($\sim \mu \mathrm{T}$) region can be achieved. Field-induced changes in frequency dependent complex permeability of the GMI microwire are measured through the IDT insertion loss due to the resulting impedance mismatch. Initial results indicate that optimizing sensor parameters enables high sensitivity in weak magnetic field detection as required for direct measurement of the internal state of batteries.