Abstract-An optimized giant magneto-impedance effect magnetometer has been developed, based upon an overall analysis of the measurement chain, including physical material properties, associated detection coil parameters, and equivalent magnetic noise performances. The field response model for the sensing element and the noise model yield good agreement with experimental results. The noise performance of the magnetometer, approximately 1.7 pT/ √ Hz in the white noise region, with a band-pass of about 70 kHz, is competitive with that of other technologies. Present limitations are clearly established, leaving room for further improvements.

Two versions of an operational giant magnetoimpedance (GMI)-based magnetometer, one of which is capable of working in an unshielded geomagnetic field, has been design, built and benchmarked against a commercial fluxgate magnetometer. The sensing element consists of a detection coil, strongly coupled to the GMI wire, in a two-port configuration. Its optimization is based on the surface impedance tensor of the sensing element, in which we include parasitic capacitance and geometric parameters of the coil. Conditions for optimizing the electronic noise level are deduced from the model recently published in IEEE Sensors Journal, 1317, 2011. The optimized sensor and its conditioning electronics are operated in a field-locked loop, using an external coil or the detection coil for feedback. Experimental noise performance correlates well with that expected from the sensitivity and noise models and are comparable to those of a commercial Flux-Gate magnetometer, offering a low-cost solution for high sensitivity magnetometry. However, the proposed GMI magnetometers still exhibit significant 1/f noise.