Signal enhancement in cantilever magnetometry based on a co-resonantly coupled sensor

Abstract

SummaryCantilever 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.

Employing electro-mechanical analogies for co-resonantly coupled cantilever sensors

“…In terms of circuit analysis, the software LTspice is used. Furthermore, we will compare the obtained results with experimental data for a co-resonantly coupled sensor, which is discussed in detail in Körner et al (2016). The sensor's properties are therefore given in Table 2.…”

“…Furthermore, we have already employed the sensor for cantilever magnetometry measurements, which proved a significant increase in sensitivity compared to magnetometry experiments with similar magnetic samples (Körner et al, 2015(Körner et al, , 2016. However, the purely mechanical description of the system is only one possibility.…”

“…Therefore, the external interaction was given by a magnetostatic interaction between the iron nanowire and a magnetic field introduced by a permanent magnet (Körner et al, 2016). The magnetic field can be estimated rather accurately by 2-D finite element simulation of the magnet with the software package FEMM (Meeker, 2015), leading to an interaction spring constant of k 3 ≈ (−2 ± 0.5) × 10 −5 Nm −1 for a magnetic field of approximately −400 mT (Körner et al, 2016). Whereas the frequency shift of the sensor has been measured in different magnetic field strengths in the experiment, we will only choose one value as an example here.…”

“…Whereas the frequency shift of the sensor has been measured in different magnetic field strengths in the experiment, we will only choose one value as an example here. The complete measured data and further experimental details are discussed in another publication (Körner et al, 2016).…”

Effective Sensor Properties of a Novel Co-Resonant Cantilever Sensor

“…Co-resonant cantilever sensors have been shown to tremendously increase the signal strength in proof-of-principle experiments in cantilever magnetometry and magnetic force microscopy (MFM) [1][2][3]. Since the measurement principle is only based on the coupling and eigenfrequency matching (termed as co-resonance) of a micro-and a nanocantilever, it could potentially by extended to other applications for dynamic-mode cantilever sensors, for example gas sensing ('artificial nose') [4] or mass sensors [5].…”