Unraveling the magnetic order in non-layered 2D materials

In this proposal, we aim to investigate the magnetic order in the ultimately thin and novel Cr2S3 and Cr2+2/3S4 compounds, the new phase of FeS, namely hexagonal Fe2S2 and in Fe-intercalated NbS2 bilayers. Our previous measurements with magnetic field dependent scanning tunneling spectroscopy (STM) on Cr2S3 and Cr2+2/3S4 demonstrate that the materials have magnetic order, but to access the Cr layer below the surface, a complementary technique such as X-ray magnetic circular dichroism is required. Test experiments for Cr2S3 at ALBA indicates the layers are antiferromagnetically coupled. Single layers of Cr2S3 are grown via molecular beam epitaxy (MBE), which allows to further forming Cr2+2/3S4, an entirely new compound consisting of 3 Cr layers sandwiched by S layers, of which one has Cr vacancies giving rise to a √3x√3R30° pattern. We have also achieved nonlayered materials via intercalation of Fe in the van-der-Waals gap of NbS2 bilayers, establishing Fe1/3Nb2S4. These structures resemble their bulk counterpart, but represent unique minimum thickness 2D materials with their magnetic properties largely unexplored.