Microfluxgate sensors for high frequency and low power applications

Low cost and low power consumption are key factors to the spreading of microsystems into the everyday life tools. Fluxgate magnetometer systems still request such an improvement. This paper presents compact thin film microfluxgate sensors working in the range of tenths of kHz to tenths of MHz which exhibit improved factor of merit (FOM) in the high frequency range when the sensor size is reduced. The architecture is based on interlaced excitation and detection solenoid coils wounded around two rectangular cores made of thin film soft magnetic sputtered NiFe permalloy material. Measurement axis and magnetic hard axis are along core length. These thin film sensors also proved to be working in a wide range of excitation currents since deep saturation is not requested thanks to a highly nonlinear hysteresis loop. Excitation currents as low as 6 mA lead to still linear output response. Devices with monolayer cores were measured up to 20 MHz. Laminated cores were measured up to 73 MHz. Frequency response higher than 100 MHz is achieved when magnetostatic coupling occurs between laminated layers. The power consumption can be monitored at system level to adjust the sensor sensitivity within a range of 0.5 to more than 220 V/T.