  The large interest in chiral magnetic structures for realization of nanoscale
magnetic storage or logic devices has necessitated methods which can quantify
magnetic interactions at the atomic scale. To overcome the limitations of the
typically used current-based sensing of atomic-scale exchange interactions, a
force-based detection scheme is highly advantageous. Here, we quantify the
atomic-scale exchange force field between a ferromagnetic tip and a cycloidal
spin spiral using our developed combination of current and exchange force
detection. Compared to the surprisingly weak spin polarization, the exchange
force field is more sensitive to atomic-scale variations in the magnetization.
First-principles calculations reveal that the measured atomic-scale variations
in the exchange force originate from different contributions of direct and
indirect (Zener) type exchange mechanisms, depending on the chemical tip
termination. Our work opens the perspective of quantifying different exchange
mechanisms of chiral magnetic structures with atomic-scale precision using 3D
magnetic exchange force field measurements.
