Multi-modal and quantitative Magnetic Force Microscopy - Application to Thin Film Systems with interfacial Dzyaloshinskii-Moriya Interaction

It has been shown that Magnetic Force Microscopy (MFM) has the potential to reach high sensitivities as well as high special resolution for the investigation of magnetic structures. Only measurements in vacuum with high Q cantilevers reveal this potential completely. In this environment the common dual pass techniques often utilized for the tip sample distance control in MFM cannot be applied.

In this work we present a method that utilizes the tip sample capacitance as a proxy for the tip sample distance. It allows for a distance feedback which is independent from other tip sample interactions and thus a simultaneous measurement of the sample's topography and the stray field of the sample in a single pass scan. Hence, it is capable to provide the precise control of the tip sample distance which is required for a calibration of the MFM tip and a subsequent quantitative analysis of the data. Especially the possibility of constant height scans where the topography is inferred from the capacitance signal is a necessary prerequisite for quantitative MFM measurements. In this measurement mode it is possible to subtract the van der Waals contribution in the measured data and to determine the magnetic part of the tip sample interaction. 

This measurement technique is applied to sputtered Ir/Co/Pt multilayer samples with interfacial Dzyaloshinskii-Moria interaction (DMI) which provides the basis for the existence of magnetic skyrmions in those films. The MFM measurements reveal a local variation of the  DMI which, since on the length scale of the skyrmion diameter,  leads to a pinning of the skyrmions.