Optimizing the sensitivity of a GMR sensor for superparamagnetic nanoparticles detection: Micromagnetic simulation

Highlights: • Micromagnetic simulations of bilayer array sensors for detecting 20 nm particles are performed. • The magnetoresistance of sensors were investigated as a function of the size and shape of the bilayers. • Sensor sensitivity can be increased by raising its bilayers aspect ratio. • A high bilayer aspect ratio increases the magnetic field for reverse magnetization. • The most sensitive sensor of those studied is the type-N BA sensor with 3200 × 200 nm² dimensions. The magnetoresistance (MR) of different sensor setups of bilayer arrays by micromagnetic simulations has been studied in order to detect 20 nm diameter Fe₃O₄ superparamagnetic nanoparticles. The MR signal of sensors with different sizes and/or different aspect ratios has been compared. We have proved that for a sensor with a given shape and size, the sensor sensitivity can be increased by raising the aspect ratio of its bilayers. The sensors can detect from hundreds down to a few tens of superparamagnetic nanoparticles randomly distributed on the sensor surface.