SEMPA investigation of the Dzyaloshinskii-Moriya interaction in the single, ideally grown Co/Pt(111) interface

The microstructure of magnetic domain walls in epitaxial, single-layer cobalt films on Pt(111) with a pseudomorphic, atomically flat interface is studied by means of scanning electron microscopy with polarization analysis. Uncapped, thermally evaporated cobalt on a clean platinum single-crystal surface is imaged in situ in ultrahigh vacuum. For a cobalt thickness of 1.4 nm we observe N\'eel-like domain walls that show a fixed, counterclockwise sense of rotation. This is indicating a strong Dzyaloshinskii-Moriya interaction (DMI) that originates from the single Co/Pt interface. The width of the domain walls has been determined as dw=(27±2)0.28em0exnm. From the observation of a pure N\'eel-like rotation, we derive a lower bound for the DMI strength of 0.5×10^-30.28em0exJ/m², which gives a DMI energy per interface atom larger than 0.8 meV. An upper bound for the DMI energy of 4.3 meV per interface atom is derived from the observation of stable domains at the onset of ferromagnetism at 0.3-nm Co thickness, corresponding to an average Co coverage of 1.5 monolayers.