Enhanced dc Magnetic Field Sensitivity for Coupled ac Magnetic Field and Stress Driven Soft Magnetic Laminate Heterostructure

Abstract

To improve the dc magnetic field sensitivity of conventional inductor-type (i.e., longitudinally driven giant magnetoimpedance) sensor at the low excitation frequency, a transformer-type laminated magnetic sensor consisting of soft magnetostrictive alloy FeBSiC/piezoelectric ceramics Pb(Zr,Ti)O3/FeBSiC heterostructure wrapped with both the exciting and sensing coils (i.e., FPFCexCse) is proposed. Compared to the inductor-type dc magnetic sensor (i.e., Hac driven FeBSiC ribbons with only exciting coils), on one hand the ac magnetic field (Hac) produced by the exciting coil and the stress produced by electrically driven PZT are synchronously coupled to enhance the magnetic induction variation of FeBSiC and the induced voltage sensitivity of sensing coils. On the other hand the mutual inductance induced voltage eliminates the weak skin effect at the low excitation frequency. When the exciting coil and PZT of FPFCexCse laminate are synchronously excited with 5 mA ac current and 5 V voltage at the mechanical resonance frequency, the maximum magnetic field sensitivity of 21200 V/T is achieved. This is about 4.08 times and 2.98 times as high as that of FeBSiC ribbon with only exciting coils (5190 V/T) and FeBSiC ribbons with both exciting and sensing coils (7120 V/T), respectively. Furthermore the equivalent magnetic noise of $114~{\mathrm {pT}}/\sqrt {{\mathrm {Hz}}} $ (at 1Hz) is achieved by the FPFC exCse laminate, which is obviously lower than that of Hac driven FeBSiC ribbons.