Artefact suppression in advanced magnetic force microscopy via integrated differential imaging

• Applicants: Dr. Thomas Mühl; Dr. Volker Neu
• Subject Area: Experimental Condensed Matter Physics ; Synthesis and Properties of Functional Materials
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 543356004

Magnetic force microscopy (MFM) has established its role as an extremely valuable method for the investigation of magnetic microstructures on the micro- and nanometer scale. Nevertheless, it still suffers from a variety of magnetic and non-magnetic artefacts, which handicap the quantitative analysis in terms of stray field gradients and sometimes even lead to a completely erroneous qualitative interpretation of the measured signal. Hence a careful assessment or even suppression of possible artefacts is in need, which is not sufficiently realized in standard MFM protocols and technology. In this proposal we will develop MFM probes with integrated switching and tuning ability, which, due to their new functionality, will allow for automatic subtraction of non-magnetic artefacts, will enable higher spatial resolution and sensitivity, and will reduce a possible disturbance of the sample’s micromagnetic state during measurement. These improvements will largely advance the quality and significance of MFM measurements of functional materials. Even additional classes of materials may become accessible to MFM, where faint magnetic responses are covered by chemical, topographical or electrostatic interactions when using state-of-the-art MFM. We will approach this objective by developing and preparing µ-coils at the end of commercial cantilevers. By a careful consideration of geometrical and thermal aspects we aim at stray field profiles with peak fields sufficient to manipulate and switch commercially available MFM tips and tailor-made high-resolution magnetic nanowire tips. This challenge that has not yet been realized in the scientific community. With a line-wise inversion of the tip’s magnetic moment, the difference signal will be free of any non-magnetic contribution. We will carefully investigate the quantitative aspects of this new differential imaging technique and finally apply these tips for artefact-free quantitative imaging of magnetic textures in curved nanostructures and to the controlled manipulation of magnetic states in a magnonic crystal. In the course of the project we will create substantial new knowledge on the generation of large magnetic fields by means of µ-coils, the role of field-inhomogeneity in magnetization reversal, magnetochiral effects in curved single crystal nanowires, and the influence of tuned local tip fields on the magnetization states in soft magnetic nanodot arrays. In addition, we will develop a technology for artefact-free MFM measurements, which will create tremendous new possibilities within the research areas of magnetism and magnetic functional materials.

• DFG Programme: Research Grants