Detection of a single magnetic dot using a Planar Hall sensor

We have successfully demonstrated the detection of pseudo-magnetic beads placed on top of 4×4 μm 2 and 5×5 μm 2 Planar Hall trilayer (Si/Co 10 nm /Cu 2 nm /NiFe 10 nm ) sensors. The sensor and the pseudo-magnetic beads were fabricated using a combination of e-beam and optical lithography techniques. Magneto-transport measurements detect the presence of dots placed on top of the PHE junction, even to the limit of single-dot. We observed that the PHE response is very sensitive to changes in the density of coverage of the sensing area with pseudo-magnetic beads. We attribute this effect to the direct coupling between the dots and the sensing layer below.