Spin Spiral State at a Ferromagnetic Gd Vacuum Interface

Here we report on the observation of a spin spiral state at the Gd(0001) surface. Spinpolarized scanning tunneling microscopy images show striped regions with a periodicity of about 2 nm.

These stripes rearrange upon application of an external magnetic field, thereby unambiguously confirming their magnetic origin. Density functional theory calculations explain that competing exchange interactions in the surface layer of Gd(0001) together with a magnetovolume fine-tuning of the exchange interaction to the next Gd layer favor a chiral 2 nm conical spin spiral at the surface, arising as a general behavior of the Gd monolayer.