Recently, magnetic nanoparticles and planar Hall resistance (PHR) devices used in biomolecule diagnosis and
biological applications have attracted considerable attention as biosensors. The voltage properties of a planar
Hall device with a Ta/NiFe/Ta/NiFe/Ta multilayer that was prepared in a cross-shaped pattern at a width of 0.5
mm using a shadow mask, were investigated. The sensitive planar Hall voltage (SPHV) obtained from the planar
Hall voltage (PHV) curves of a Ta(5 nm)/NiFe(6 nm)/Ta(t = 2-8 nm)/NiFe(6 nm)/Ta(5 nm) multilayered
sample was a few mV/Oe in the fine magnetic field region of the external magnetic field of ± 1.0 Oe. In particular,
the thickness of Ta(t = 8 nm), the PHR ratio, magnetic sensitivity, and SPHV improved significantly by as
much as 36.4 %, 28 %/Oe, and 1.6 mV/Oe, respectively. These results can be used in the development of a PHR
biosensor with a high sensitivity for the detection of nanoparticle-antibody binding, even in a simple structure
formed only out of a ferromagnetic NiFe layer.