Optimization of spin-valve parameters for magnetic bead trapping and manipulation

Published

February 6, 2010

Author(s)

Wendy R. Altman, John M. Moreland, Stephen E. Russek, Victor M. Bright

Abstract

Magneto-optic Kerr effect (MOKE) and magnetoresistance (MR) measurements were used to measure the switching characteristics of spin-valve (SV) arrays currently being developed to trap and release superparamagnetic beads within a fluid medium. The effect of SV size on switching observed by MOKE showed that a 1 υm x 8 υm SV element was found to have optimal switching characteristics. MR measurements on a single 1 υm x 8 υm SV switched with either an external applied magnetic field or a local magnetic field generated by an integrated write wire (current density ranging from 10⁶ to 10⁷ A/cm²) confirmed the MOKE findings. The 1 υm x 8 υm SV low field switching was observed to be +8 and -2 mT with two stable states at zero field; the high field switching was observed to be -18 mT. The low switching fields and the large magnetic moment of the SV trap along with our observation of minimal magnetostatic effect for dense arrays are necessary design characteristics for high-force, "switchable-magnet," microfluidic bead trap applications.

Citation

Journal of Magnetism and Magnetic Materials

Volume

322

Pub Type

Journals

Keywords

spin-valve, magnetic beads, microfluidic, magnetic manipulation, switchable magnetic trap

Citation

Altman, W. , Moreland, J. , Russek, S. and Bright, V. (2010), Optimization of spin-valve parameters for magnetic bead trapping and manipulation, Journal of Magnetism and Magnetic Materials (Accessed October 8, 2025)