Resonance-Based Detection of Magnetic Nanoparticles and Microbeads Using Nanopatterned Ferromagnets

Manu Sushruth, Junjia Ding, Jeremy Duczynski, Robert C. Woodward, Ryan A. Begley, Hans Fangohr, Rebecca O. Fuller, Adekunle O. Adeyeye, Mikhail Kostylev, and Peter J. Metaxas
Phys. Rev. Applied 6, 044005 – Published 5 October 2016
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Abstract

Biosensing with ferromagnet-based magnetoresistive devices has been dominated by electrical detection of particle-induced changes to a device’s (quasi-)static magnetic configuration. There are however potential advantages to be gained from using field dependent, high frequency resonant magnetization dynamics for magnetic particle detection. Here, we demonstrate the use of nanoconfined ferromagnetic resonances in periodically nanopatterned magnetic films for the detection of adsorbed magnetic particles having diameters ranging from 6 nm to 4μm. The nanopatterned films contain arrays of holes which appear to act as preferential adsorption sites for small particles. Hole-localized particles act in unison to shift the frequencies of the patterned layer’s ferromagnetic-resonance modes, with shift polarities determined by the localization of each mode within the nanopattern’s repeating unit cell. The same polarity shifts are observed for a large range of coverages, even when quasicontinuous particle sheets form above the hole-localized particles. For large particles, preferential adsorption no longer occurs, leading to resonance shifts with polarities that are independent of the mode localization, and amplitudes that are comparable to those seen in continuous layers. Indeed, for nanoparticles adsorbed onto a continuous layer, the particle-induced shift of the layer’s fundamental mode is up to 10 times less than that observed for nanoconfined modes in the nanopatterned systems, the low shift being induced by relatively weak fields emanating beyond the particle in the direction of the static applied field. This result highlights the importance of having particles consistently positioned in the close vicinity of confined modes.

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  • Received 28 June 2016

DOI:https://doi.org/10.1103/PhysRevApplied.6.044005

© 2016 American Physical Society

Physics Subject Headings (PhySH)

Physics of Living SystemsCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Manu Sushruth1, Junjia Ding2,*, Jeremy Duczynski3, Robert C. Woodward1, Ryan A. Begley1, Hans Fangohr4, Rebecca O. Fuller3, Adekunle O. Adeyeye2, Mikhail Kostylev1, and Peter J. Metaxas1,†

  • 1School of Physics, M013, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
  • 2Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576, Singapore
  • 3School of Chemistry and Biochemistry, M310, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
  • 4Faculty of Engineering and the Environment, University of Southampton, Southampton SO17 1BJ, United Kingdom

  • *Present address: Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439, USA.
  • peter.metaxas@uwa.edu.au

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Issue

Vol. 6, Iss. 4 — October 2016

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