Detection of a single magnetic dot using a Planar Hall sensor

Abstract

We have successfully demonstrated the detection of pseudo-magnetic beads placed on top of 4×4 μm2 and 5×5 μm2 Planar Hall trilayer (Si/Co10 nm /Cu2 nm /NiFe10 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. © 2006 Elsevier B.V. All rights reserved.