| Combined with magnetic labeling, Giant Magnetoresistance (GMR) sensors can be used in biosensors. For applications in diagnosis by detecting the areal density of magnetic microbeads, NiFeCo/Cu multilayers were studied. Firstly, GMR effect was introduced, including the definition of GMR, its theory explanation and model, and several GMR structures. NiFeCo/Cu multilayers were prepared by magnetron sputtering. Dependences of GMR on buffer layer thickness, nonmagnetic layer thickness, and magnetic layer thickness were studied. NiFeCo/Cu multilayers with low saturation field and small hysteresis were obtained. Principles of GMR sensor were analyzed. Dipole field of single magnetic bead and its signal were calculated. GMR sensors were fabricated by photolithography, sputtering, RIE etc. Tests were done. In conclusion the NiFeCo/Cu multilayers can be used in biosensors and the GMR sensors can detect magnetic microbeads. |
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