Detection of single micron-sized magnetic bead and magnetic nanoparticles using spin valve sensors for biological applications
- Resource Type
- Authors
- Ronald W. Davis; Vikram Joshi; Chris D. Webb; Robert L. White; Jennifer T. Kemp; Shouheng Sun; Shan X. Wang; Guanxiong Li
- Source
- Journal of Applied Physics. 93:7557-7559
- Subject
- Materials science
Magnetoresistance
business.industry
Spin valve
Analytical chemistry
General Physics and Astronomy
equipment and supplies
Biomagnetism
Magnetic field
Magnetization
Optoelectronics
Magnetic nanoparticles
business
human activities
Magnetic dipole
Superparamagnetism
- Language
- ISSN
- 1089-7550
0021-8979
We have fabricated a series of highly sensitive spin valve sensors on a micron scale that successfully detected the presence of a single superparamagnetic bead (Dynabeads M-280, 2.8 μm in diameter), and thus showed suitability for identifying biomolecules labeled by such magnetic beads. By polarizing the magnetic microbead on a spin valve sensor with a dc magnetic field and modulating its magnetization with an orthogonal ac magnetic field, we observed a magnetoresistance (MR) signal reduction caused by the magnetic dipole field from the bead that partially cancelled the applied fields to the spin valve. A lock-in technique was used to measure a voltage signal due to the MR reduction. A signal of 1.2 mV rms or 5.2 mΩ of resistance reduction was obtained from a 3 μm wide sensor and a signal of 3.8 mV rms or 11.9 mΩ from a 2.5 μm wide sensor. Micromagnetic simulations were also performed for the spin valve sensors with a single bead and gave results consistent with experiments. Further experiments and simula...