Dependence of sensitivity and noise of fluxgate sensors on racetrack geometry

Small, racetrack shaped fluxgate-sensors with a core of (CoFe)₇₀(MoSiB)₃₀ amorphous metal tape are optimized in geometry to achieve a high sensitivity to external magnetic fields and low intrinsic white noise. For optimization we employed statistical methods of experimental design. We varied the length, the width and the number of tape layers in the core keeping constant the peak magnetization during the magnetic field modulation. Numerical simulations help us to understand the interaction of sensor core geometry and the observed sensitivity and noise. The best white noise level is below √(S_B)(1 kHz)=400 fT/√(Hz). This noise level has so far been achieved with small sensors only by SQUIDs. We discuss the consequences of the geometry influence on the miniaturization of fluxgate sensors