Micromagnetic Modeling of a GMR Vortex Sensor for the Detection of Superparamagnetic Labels

Developing efficient solutions for POC diagnostics is a topical issue in biomedicine since reliable POC testing safes laboratory capacities and helps treating infections more quickly. POC tests can be realized in single chips that exploit the mechanisms of microfluidics and bring all laboratory steps to a single chip for quantifying a specific molecule. In magnetic systems, the final detection is accomplished by magnetoresistive sensors that detect the magnetic stray field of a label, biochemically connected to the molecule to enhance the magnetic stray field. For labels in the nanometer range, a lownoise approach is essential due to the weak magnetic stray field. Accordingly, this work presents a sensor concept that enables low-noise detection of labels assigned to the nanometer range. A standard GMR structure is upgraded with magnetic vortex structures to minimize any noise contributions. Using micromagnetic simulations fundamental effects are analyzed and the sensor response is approximated for different label configurations. The results reinforce the intention to implement such a sensor concept in a microfluidic system for the detection of superparamagnetic labels.