Reorientation of the diagonal double-stripe spin structure at Fe1+yTe bulk and thin-film surfaces

Establishing the relation between ubiquitous antiferromagnetism in the parent compounds of unconventional superconductors and their superconducting phase is important for understanding the complex physics in these materials. Going from bulk systems to thin films additionally affects their phase diagram. For Fe 1+ y Te, the parent compound of Fe 1+ y Se 1− x Te x superconductors, bulk-sensitive neutron diffraction revealed an in-plane oriented diagonal double-stripe antiferromagnetic spin structure. Here we show by spin-resolved scanning tunnelling microscopy that the spin direction at the surfaces of bulk Fe 1+ y Te and thin films grown on the topological insulator Bi 2 Te 3 is canted out of the high-symmetry directions of the surface unit cell resulting in a perpendicular spin component, keeping the diagonal double-stripe order. As the magnetism of the Fe d -orbitals is intertwined with the superconducting pairing in Fe-based materials, our results imply that the superconducting properties at the surface of the related superconducting compounds might be different from the bulk. Knowledge of the spin structure in parent compounds of unconventional superconductors is crucial for an understanding of the complex physics in these materials. Here, the authors report canted spin structure on the surface as well as on the thin film form of Fe 1+ y Te, different from the bulk.