Microfluxgate Sensors for High Frequency and Low Power Applications

Cost and power consumption are key factors to the spreading of microsystems into the everyday life tools. Fluxgate sensor based magnetometer systems still request such an improvement. This paper presents thin film sensor measured up to 20 MHz for a first device with solenoid coils wounded around cores made of thin monolayer of soft magnetic sputtered Ni₈₂Fe₁₈. Devices with laminated cores were measured up to 73 MHz. Frequency response higher than 100 MHz is achieved when magnetostatic coupling occurs between thin layers. Measurement axis and magnetic hard axis are along core lengths. The monolayer core sensor noise floor is below 5 nT/radicHz at 10 Hz. Compact thin film fluxgates working in the range of tenths of kHz to tenths of MHz lead to a multi-axis system able to tune intrinsic sensitivity in a 0.5 to 190 V/T range: the power consumption is monitored to dynamically reach a target resolution.