Spin-spiral structures in free-standing Fe(110) monolayers

Electronic and magnetic structures in spin-spiral structures of free-standing Fe(110) monolayers with lattice constants, a, matching those of bulk bcc Fe (2.87 Å) and W (3.16 Å), were investigated by means of first-principles film full-potential linearized augmented-plane-wave calculations including intra-atomic noncollinear magnetism. For a=2.87 Å, the spin-spiral structures with wavelength around 7a are energetically favored over the collinear ferromagnetic state while those for a=3.16 Å turn out to be less favorable. The formation of the spin-spiral structures are found to result from a Fermi-surface nesting that leads to an instability of the ferromagnetic state. In addition, the spin-orbit coupling is found to play an important role to determine the magnetization rotation. These results offer an important step in understanding complex noncollinear spin-spiral magnetism in thin films.