Giant magnetoresistive spin valve bridge sensor

We describe the design, fabrication, and performance of a ''spin valve'' magnetic field sensor based on the giant magnetoresistive effect. The sensor is a balanced, four resistor, fully biased, Wheatstone bridge network with bipolar output. The devices described here show magnetoresistance ratios Delta V/V = Delta R/R = 6%, saturation fields of 25 Oe, and a Johnson limited noise floor of 2.6 mu Oe/(Hz)(1/2). The linearity of the device is +/-2% of the full scale amplitude, with a hysteresis of 1% over the linear range. Fabrication of this device requires a novel approach to setting the directions of the antiferromagnetic exchange layers that bias the sensor. As compared to bridges based on the anisotropic magnetoresistance effect, these devices offer superior signal amplitude and linearity. To our knowledge this is the first report of such a device.