Abstract
Cantilever magnetometry is a measurement technique used to study magnetic nanoparticles. With decreasing sample size, the signal strength is significantly reduced, requiring advances of the technique. Ultrathin and slender cantilevers can address this challenge but lead to increased complexity of detection. We present an approach based on the co-resonant coupling of a micro- and a nanometer-sized cantilever. Via matching of the resonance frequencies of the two subsystems we induce a strong interplay between the oscillations of the two cantilevers, allowing for a detection of interactions between the sensitive nanocantilever and external influences in the amplitude response curve of the microcantilever. In our magnetometry experiment we used an iron-filled carbon nanotube acting simultaneously as nanocantilever and magnetic sample. Measurements revealed an enhancement of the commonly used frequency shift signal by five orders of magnitude compared to conventional cantilever magnetometry experiments with similar nanomagnets. With this experiment we do not only demonstrate the functionality of our sensor design but also its potential for very sensitive magnetometry measurements while maintaining a facile oscillation detection with a conventional microcantilever setup.
Highlights
Over the last decade, magnetic objects of micro- and nanometer size have come into focus of researchers, since they offer a wide range of possible applications
Measurements revealed an enhancement of the commonly used frequency shift signal by five orders of magnitude compared to conventional cantilever magnetometry experiments with similar nanomagnets
It has been shown previously that a filled carbon nanotube (FeCNT) oscillating in a magnetic field without being placed onto a cantilever can exhibit a large frequency shift compared to the field-free case
Summary
Magnetic objects of micro- and nanometer size have come into focus of researchers, since they offer a wide range of possible applications. In order to obtain them for the given sensor geometry we will be using an approximate formula to calculate the expected resonance angular frequencies of the coupled system ωa/b = 2πfa/b for a small interaction spring constant k3[17]: fa/b field-free Position 1 fa/b @ 406 mT Δf Position 2 fa/b @ −406 mT Δf
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