Accurate determination of MFM tip’s magnetic parameters on nanoparticles by decoupling the influence of electrostatic force

Abstract

Magnetic force microscopy (MFM) has become one of the most important instruments for characterizing magnetic materials with nanoscale spatial resolution. When analyzing magnetic particles by MFM, calibration of the magnetic tips using reference magnetic nanoparticles is a prerequisite due to similar orientation and dimension of the yielded magnetic fields. However, in such a calibration process, errors caused by extra electrostatic interactions will significantly affect the output results. In this work, we evaluate the magnetic moment and dipole radius of the MFM tip on Fe3O4 nanoparticles by considering the associated electrostatic force. The coupling of electrostatic contribution on the measured MFM phase is eliminated by combining MFM and Kelvin probe force microscopy together with theoretical modeling. Numerical simulations and experiments on nickel nanoparticles demonstrate the effectiveness of decoupling. Results show that the calibrated MFM tip can enable a more accurate analysis of micro-and-nano magnetism. In addition, a fast and easy calibration method by using bimodal MFM is discussed, in which the acquisition of multiple phase shifts at different lift heights is not required.

A Review of the Current State of Magnetic Force Microscopy to Unravel the Magnetic Properties of Nanomaterials Applied in Biological Systems and Future Directions for Quantum Technologies

“…forces [247]. The magnetic force between a tip, which in the dipole approximation, has a fixed magnetic moment mtip, and the sample is due to the gradient of the stray field Bstray generated by surface and volume magnetic charges [248]:…”

“…The van der Waals force is short-ranged but is more potent than electrostatic and magnetic forces. Thus, it is essential to position the AFM probe at least 30–50 nm above the topography scan (see Section 4 for more details) to account for the long-range magnetic forces [ 247 ]. The magnetic force between a tip, which in the dipole approximation, has a fixed magnetic moment m tip , and the sample is due to the gradient of the stray field B stray generated by surface and volume magnetic charges [ 248 ]: where the cantilever displacement is normal to the sample.…”