Microfluxgate sensor with amorphous cobalt (Co–Nb–Zr) soft magnetic core for electronic compass

Abstract

A silicon based microfluxgate sensor with a cobalt based amorphous soft magnetic core for electronic compass is presented in this paper. A sputtered Co85Nb12Zr3 magnetic core having a rectangular ring shape is combined with microcopper solenoid coils for excitation and pickup, which were wound alternately around the core to increase the number of coil turns. The Co85Nb12Zr3 as a core material is adopted for improving properties of the magnetic core and easy integration with micromachining processes to achieve a small size of the sensor. The sputtered Co85Nb12Zr3 showed dc effective permeability of ∼10000 and an extremely low coercivity of ∼0.03Oe with the thickness of 1μm. The Co85Nb12Zr3 as a thin film core with high permeability and low coercivity was easily saturated by a low excitation magnetic field, enhancing the sensitivity and linearity of the microfluxgate sensor. Finally, the sensor showed excellent linearity response over the range of −300 to 300μT with sensitivity of 60V∕T at the excitation condition of 3.0Vp-p and 5.0 MHz square wave form. The sensor size excluding pad region is about 0.55×1.4mm2.