Exchange-biased planar Hall effect sensor optimized for biosensor applications

This article presents experimental investigations of exchange-biased Permalloy planar Hall effect sensor crosses with a fixed active area of w x w = 40 x 40 mu m(2) and Permalloy thicknesses of t = 20, 30, and 50 nm. It is shown that a single domain model describes the system well and that the thicker film will have a higher signal as well as a lower noise. It is estimated that the signal-to-noise ratio for bead detection increases by a factor 2.1 when t is increased from 20 to 50 nm and hence a higher t is beneficial for biosensor applications. This is exemplified with calculations on M-280 Dynabeads (R).