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On-chip measurement of the Brownian relaxation frequency of magnetic beads using magnetic tunneling junctions

2011; American Institute of Physics; Volume: 98; Issue: 7 Linguagem: Inglês

10.1063/1.3554374

1520-8842

Marco Donolato, Elisa Sogne, Bjarke Thomas Dalslet, M. Cantoni, D. Petti, Jiangwei Cao, Filipe A. Cardoso, Susana Cardoso, P. P. Freitas, Mikkel Fougt Hansen, R. Bertacco,

Magnetic properties of thin films

We demonstrate the detection of the Brownian relaxation frequency of 250 nm diameter magnetic beads using a lab-on-chip platform based on current lines for exciting the beads with alternating magnetic fields and highly sensitive magnetic tunnel junction (MTJ) sensors with a superparamagnetic free layer. The first harmonic out-of-phase component of the MTJ response gives the imaginary part of the magnetic bead susceptibility, which peaks at the Brownian relaxation frequency. This work paves the way to on-chip implementation of Brownian magnetorelaxometry in innovative “lab-on-a-bead” assays for biomolecular recognition.