Dependence of sensitivity and noise of fluxgate sensors on racetrack geometry

Small, racetrack shaped fluxgate-sensors with a core of (CoFe)(70)(MoSiB)(3 0) amorphous metal tape are optimized in geometry to achieve a high sensiti vity to external magnetic fields and low intrinsic white noise. For optimiz ation we employed statistical methods of experimental design. We varied the length, the width and the number of tape layers in the core keeping consta nt the peak magnetization during the magnetic field modulation. Numerical s imulations help us to understand the interaction of sensor core geometry an d the observed sensitivity and noise. The best white noise level is below r ootS(B) (1 kHz) = 400 fT/root Hz. This noise level has so far been achieved with small sensors only by Superconducting Quantum Interference Devices. W e discuss the consequences of the geometry influence on the miniaturization of fluxgate sensors.