Origin of electric-field-induced modification of magnetocrystalline anisotropy at Fe(001) surfaces: Mechanism of dipole formation from first principles

First-principles full-potential linearized augmented plane-wave studies reveal that a surface magnetocrystalline anisotropy (MCA) modification by an external electric field arises from a dipole formation mechanism. The precise calculations demonstrate that the formation of dipoles on Fe(001) surface atoms, which counteract the electric-field-induced charge in the vacuum region, changes the surface states around the Fermi level in the minority-spin d bands, and yields a modification of the surface MCA. These findings greatly advance our understanding of the electric-field-induced MCA modifications in itinerant ferromagnetic surfaces.