Optimizing magnetoresistive sensor signal-to-noise via pinning field tuning

The presence of magnetic noise in magnetoresistive-based magnetic sensors degrades their detection limit at low frequencies. In this paper, different ways of stabilizing the magnetic sensing layer to suppress magnetic noise are investigated by applying a pinning field, either by an external field, internally in the stack, or by shape anisotropy. We show that these three methods are equivalent, could be combined, and that there is a competition between noise suppression and sensitivity reduction, which results in an optimum total pinning field for which the detection limit of the sensor is improved up to a factor of 10.The presence of magnetic noise in magnetoresistive-based magnetic sensors degrades their detection limit at low frequencies. In this paper, different ways of stabilizing the magnetic sensing layer to suppress magnetic noise are investigated by applying a pinning field, either by an external field, internally in the stack, or by shape anisotropy. We show that these three methods are equivalent, could be combined, and that there is a competition between noise suppression and sensitivity reduction, which results in an optimum total pinning field for which the detection limit of the sensor is improved up to a factor of 10.