Effect of Thickness of Electroplated NiFe Cores on the Noise of Fluxgates

In this paper we present the effect of the thickness on the field-induced anisotropy of NiFe layers. We electroplated several ring-cores with thickness spanning from 2 μm to 18 μm changing the deposition time (and keeping unchanged the other parameters). The ring-cores were placed during the electroplating process in yoke, which produced 720 kA/m radial field in order to induce a radial anisotropy to the ring. We observed that the field-induced anisotropy significantly increases up to 12 μm thickness; for further increment of thickness the anisotropy does not increase anymore. The effect is visible on the noise of the fluxgate based on such rings: the noise quickly drops for increase of thickness due to larger radial anisotropy. However, for 18 μm the noise slightly rises due to emerging of demagnetizing effect. Therefore we derive that 12 μm is the best trade-off between the need of larger field-induced anisotropy and low demagnetization