Electric Contributions to Magnetic Force Microscopy Response from Graphene and MoS2 Nanosheets

TL;DR

This study investigates the origins of magnetic force microscopy signals from graphene and MoS2 nanosheets, revealing that electric artefacts, not magnetism, primarily cause the observed signals.

Contribution

It systematically demonstrates that MFM signals from these nanosheets are dominated by electric interactions, challenging previous claims of magnetism based on MFM data.

Findings

MFM signals are mainly due to electric artefacts, not magnetism.

Electric force microscopy confirms significant electrostatic contributions.

MFM signals do not respond to reversed magnetic fields.

Abstract

Magnetic force microscopy (MFM) signals have recently been detected from whole pieces of mechanically exfoliated graphene and molybdenum disulfide (MoS2) nanosheets and magnetism of the two nanomaterials was claimed based on these observations. However, non-magnetic interactions or artefacts are commonly associated with MFM signals, which makes the interpretation of MFM signals not straightforward. A systematic investigation has been done to examine possible sources of the MFM signals from graphene and MoS2 nanosheets and whether the MFM signals can be correlated with magnetism. It is found that the MFM signals have significant non-magnetic contributions due to capacitive and electrostatic interactions between the nanosheets and conductive cantilever tip, as demonstrated by electric force microscopy (EFM) and scanning Kevin probe microscopy (SKPM) analyses. In addition, the MFM signals of graphene and MoS2 nanosheets are not responsive to reversed magnetic field of the magnetic cantilever tip. Therefore, the observed MFM response is mainly from electric artefacts and not compelling enough to correlate with magnetism of graphene and MoS2 nanosheets.