24 Nov 2016 : Peter Metaxas

Thu 24 Nov 2016 – 3:30 pm (Murdoch University, Postgrad Suite ECL2.031)

Towards frequency-based electronic bio-detection at the nano-scale

Dr Peter Metaxas — School of Physics, University of Western Australia

Magnetic biosensing exploits chemically functionalised magnetic nanoparticles for labelling and subsequent detection of analytes of interest in biological samples, opening routes to new technologies for point-of-care medical diagnostics [1]. Many solid state nanoparticle detection techniques are voltage-level based. For example, in conventional magnetoresistive sensors, the magnetic configuration within the device is modified by the nanoparticles’ stray magnetic fields, generating a change in the device resistance (and thus the voltage across the device). In contrast, electrically probed, field-dependent magnetisation dynamics in magnetic nanostructures offer a route towards intrinsically frequency-based electronic biosensing. This resonance-based approach potentially offers high speed sensing with nano-scale devices [2] which can operate under very large magnetic field ranges [3]. We demonstrate the potential of this approach first using large area, periodically nanostructured ferromagnets (“magnonic crystals”) [3,4]. These systems enable us to probe the effect of nanoparticles on ferromagnetic resonances that are confined to regions in the crystal with lateral dimensions on the order of 100 nm. Secondly we look at nanoparticle sensing exploiting the “gyrotropic” resonance of ferromagnetic vortices. We show how the localized field of a nanoparticle can stiffen the vortex, leading to field sensitivities exceeding those conventionally measured in uniform fields [5]. Finally, we experimentally demonstrate spintronic, frequency-based detection of superparamagnetic beads and discuss future directions of this work (e.g. [5]).

This work would not have been possible without contributions from collaborators at the the Unité Mixte de Physique CNRS/Thales (France), University of Southampton (UK), the National University of Singapore and AIST (Japan).

[1] Gaster et al., Nat. Med., 15, 1327 (2009). [2] Braganca et al., Nanotechnol., 21, 235202 (2010). [3] Sushruth et al., Phys. Rev Appl., 6, 044005 (2016).  [4] Metaxas et al., Appl. Phys. Lett. 106, 232406 (2015).  [4] Fried and Metaxas, Phys. Rev. B, 93, 064422 (2016). [5] Albert et al., Nanotechnol. 27, 455502 (2016).


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