Sensing magnetic nanoparticles using nano-confined ferromagnetic resonances in a magnonic crystal

TL;DR

This paper presents a novel method for detecting magnetic nanoparticles by observing shifts in ferromagnetic resonances within a magnonic crystal, enabling high-speed nanoscale biosensing.

Contribution

It introduces a new approach using nano-confined ferromagnetic resonances in a magnonic crystal for magnetic nanoparticle detection, demonstrating measurable resonance shifts.

Findings

Resonance shifts are comparable to linewidths at high anti-dot filling fractions.

Resonance shifts depend on mode localization, matching micromagnetic simulations.

The method shows promise for high-speed nanoscale biosensing applications.

Abstract

We demonstrate the use of the magnetic-field-dependence of highly spatially confined, GHz-frequency ferromagnetic resonances in a ferromagnetic nanostructure for the detection of adsorbed magnetic nanoparticles. This is achieved in a large area magnonic crystal consisting of a thin ferromagnetic film containing a periodic array of closely spaced, nano-scale anti-dots. Stray fields from nanoparticles within the anti-dots modify resonant dynamic magnetisation modes in the surrounding magnonic crystal, generating easily measurable resonance peak shifts. The shifts are comparable to the resonance linewidths for high anti-dot filling fractions with their signs and magnitudes dependent upon the modes' localisations (in agreement with micromagnetic simulation results). This is a highly encouraging result for the development of frequency-based nanoparticle detectors for high speed nano-scale biosensing.