Tip-induced artifacts in magnetic force microscopy images

Abstract

Useful sample information can be extracted from the dissipation in frequency modulation atomic force microscopy due to its correlation to important material properties. It has been recently shown that artifacts can often be observed in the dissipation channel, due to the spurious mechanical resonances of the atomic force microscope instrument when the oscillation frequency of the force sensor changes. In this paper, we present another source of instrumental artifacts specific to magnetic force microscopy (MFM), which is attributed to a magnetization switching happening at the apex of MFM tips. These artifacts can cause a misinterpretation of the domain structure in MFM images of magnetic samples.

Spin configuration in isolated FeCoCu nanowires modulated in diameter

“…Figure 3 In order to gain information about the magnetic behavior of individual NWs, MFM imaging was performed with a Nanotec Electrónica system making use of the amplitude modulation (AM) and two-pass modes; in addition, a phase-locked loop (PLL) was enabled to track the resonance frequency of the oscillating cantilever (k≈3 N/m, f 0 ≈75 kHz). The existence of eventual artifacts generated by the overlap of electrostatic interactions 21 can be ruled out, as deduced from Kelvin probe force microscopy experiments (not shown); similarly, effects associated to irreversible tipsample influence 22 were not relevant. MFM was implemented at low scan speed, allowing the lock-in amplifier to filter out the majority of noise sources and yielding high resolution 23 For each of the three simulated NWs square hysteresis loops were obtained (inset in fig.…”

Superparamagnetic versus blocked states in aggregates of Fe3−xO4 nanoparticles studied by MFM

“…15,16,27,28 In order to confirm the SPM character of the aggregates of R11 NPs, a study of the dependence of the frequency shift on the tip-sample distance was carried out and the results are shown in Fig. Therefore, care must be taken to avoid misinterpretation of the MFM data, as has been previously reported.…”

Magnetic imaging using geometrically constrained nano-domain walls

“…However, smaller and more complex nanostructures require not only higher resolution MFM, but also the ability to extract detailed and accurate information about the magnetization of the sample with minimal invasiveness. Thus, the main challenges that modern MFM technology is facing are i) to increase the sensitivity (both magnetic sensitivity and spatial resolution) 7 and ii) to minimize the mutual interference between the probe and sample magnetization [8][9][10][11] . The latter requirement translates naturally into the need to use low magnetic moment probes with high coercivity.…”

“…Thereby, the most common scenario is to use a probe matching sample -probe properties in each particular case. However, this approach becomes impractical when the sample under study is magnetically heterogeneous, comprised of areas with high and low anisotropy and magnetization, or with magnetic domain walls (DWs) generating high gradient stray fields 9 . These M scenarios are more and more frequent situations faced by modern cutting-edge nanotechnology 21 , arising from both the continuous reduction in size and the use of composite, multifunctional materials that are characterized by intrinsically large heterogeneity of properties.…”