A biochip sensor based on giant and tunnel magnetoresistance

Summary form only given. Compared to the established fluorescent labeling method, the use of magnetic markers in biochip sensors has important advantages with respect to the detection of biomolecules at low concentrations. The magnetic markers are commercially available superparamagnetic microspheres. We demonstrate the applicability and functionality of both Giant Magnetoresistance (GMR) and Tunnel Magnetoresistance (TMR) sensors for detecting magnetic markers, also including corresponding molecular binding results with DNA. The GMR sensors consist of patterned Cu/NiFe multilayers in the second antiferromagnetic maximum, whose resistance vs. field dependencies can be tailored for large sensitivity (up to 3%/Oe). The experimental data are supported and understood by numerical simulations in a local field approach. Initial experiments with TMR sensors take advantage of the larger signal amplitude of around 40% and corresponding sensitivity of 12%/Oe.