Abstract
The Planar Hall effect in a spin valve structure has been applied as a biosensor being capable of detecting $Dynabeads^{(R)}$ M-280. The sensor performance was tested under the application of a DC magnetic field where the output signals were obtained from a nanovoltmeter. The sensor with the pattern size of $50{\times}100{\mu}m^2$ has produced high sensitivity; especially, the real-time profiles by using that sensor revealed significant performance at external applied magnetic field of around 7.0 Oe with the resolution of 0.04 beads per $\mu m^2$. Finally, a successful array including 24 patterns with the single sensor size of $3{\times}3{\mu}m^2$ has shown the uniform and stable signals for single magnetic bead detection. The comparison of this sensor signal with the others has proved feasibility for biosensor application. This, connecting with the advantages of more stable and high signal to noise of PHR sensor's behaviors, can be used to detect the biomolecules and provide a vehicle for detection and study of other molecular interaction.