Suppression of Barkhausen Noise in Magnetoresistive Sensors Employing AC Bias

A magnetic field rotating in the plane of a thin-film magnetoresistive sensor provides continuous saturation of the ferromagnetic material if the magnitude of the field was sufficiently large. This mode of excitation allows operation free of errors related to remanence and in the same time it helps in suppressing the Barkhausen noise. The experiment demonstrates that the contribution of the magnetic noise in the sensor output is negligible when the period of the field rotation is less than 1 ms. This enables resolution of dc and low-frequency magnetic fields of the order of 10⁻¹⁰ T/√HZ. This result can be improved by decreasing the sensor induced anisotropy and a resolution of 10⁻¹¹–10⁻¹² T/√Hz might be attainable.