Marcus Heide

First-principles analysis of a homochiral cycloidal magnetic structure in a monolayer Cr on W(110)

The magnetic structure of a Cr monolayer on a W(110) substrate is investigated by means of first-principles calculations based on noncollinear spin density functional theory (DFT). As magnetic ground state we find a long-period homochiral left-rotating spin spiral on top of an atomic-scale antiferromagnetic order of nearest-neighbor atoms. The rotation angle of the magnetic moment changes inhomogeneously from atom to atom across the spiral. We predict a propagation direction along the crystallographic

Real-space electronic structure calculations with full-potential all-electron precision for transition metals

[001]

Role of Dzyaloshinskii-Moriya interaction for magnetism in transition-metal chains at Pt step-edges

direction with a period length of

Spin–orbit induced local band structure variations revealed by scanning tunnelling spectroscopy

|\ensuremath{\lambda}|=14.3\phantom{\rule{0.16em}{0ex}}\mathrm{nm}

Dzyaloshinskii-Moriya interaction accounting for the orientation of magnetic domains in ultrathin films: Fe/W(110)

, which is in excellent agreement with a modulation of the local antiferromagnetic contrast observed in spin-polarized scanning tunneling microscope experiments by Santos et al. [New J. Phys. 10, 013005 (2008)]. We identify the Dzyaloshinskii-Moriya interaction as the origin of the homochiral magnetic structure, competing with the Heisenberg-type exchange interaction and magnetocrystalline anisotropy energy. From DFT calculations we extract parameters for a micromagnetic model and thereby determine a considerable inhomogeneity of the spin spiral, increasing the period length by 6% compared to homogeneous spin spirals. The results are compared to the behavior of a Mn and Fe monolayer and Fe double layer on a W(110) substrate.

Atomic-scale spin spiral with a unique rotational sense: Mn monolayer on W(001).

We have developed an efficient computational scheme utilizing the real-space finite-difference formalism and the projector augmented-wave (PAW) method to perform precise first-principles electronic-structure simulations based on the density functional theory for systems containing transition metals with a modest computational effort. By combining the advantages of the time-saving double-grid technique and the Fourier filtering procedure for the projectors of pseudopotentials, we can overcome the egg box effect in the computations even for first-row elements and transition metals, which is a problem of the real-space finite-difference formalism. In order to demonstrate the potential power in terms of precision and applicability of the present scheme, we have carried out simulations to examine several bulk properties and structural energy differences between different bulk phases of transition metals, and have obtained excellent agreement with the results of other precise first-principles methods such as a plane wave based PAW method and an all-electron full-potential linearized augmented plane wave (FLAPW) method.

Self-Assembled Nanometer-Scale Magnetic Networks on Surfaces: Fundamental Interactions and Functional Properties

We explore the emergence of chiral magnetism in one-dimensional monatomic Mn, Fe, and Co chains deposited at the Pt(664) step-edge carrying out an ab-initio study based on density functional theory (DFT). The results are analyzed employing several models: (i) a micromagnetic model, which takes into account the Dzyaloshinskii-Moriya interaction (DMI) besides the spin stiffness and the magnetic anisotropy energy, and (ii) the Fert-Levy model of the DMI for diluted magnetic impurities in metals. Due to the step-edge geometry, the direction of the Dzyaloshinskii vector (D-vector) is not predetermined by symmetry and points in an off-symmetry direction. For the Mn chain we predict a long-period cycloidal spin-spiral ground state of unique rotational sense on top of an otherwise atomic-scale antiferromagnetic phase. The spins rotate in a plane that is tilted relative to the Pt surface by

Describing Dzyaloshinskii–Moriya spirals from first principles

62^\circ

Spin-polarized electron scattering at single oxygen adsorbates on a magnetic surface

towards the upper step of the surface. The Fe and Co chains show a ferromagnetic ground state since the DMI is too weak to overcome their respective magnetic anisotropy barriers. Beyond the discussion of the monatomic chains we provide general expressions relating ab-initio results to realistic model parameters that occur in a spin-lattice or in a micromagnetic model. We prove that a planar homogeneous spiral of classical spins with a given wave vector rotating in a plane whose normal is parallel to the D-vector is an exact stationary state solution of a spin-lattice model for a periodic solid that includes Heisenberg exchange and DMI. The validity of the Fert-Levy model for the evaluation of micromagnetic DMI parameters and for the analysis of ab-initio calculations is explored for chains. The results suggest that some care has to be taken when applying the model to infinite periodic one-dimensional systems.

Magnetic domain walls in ultrathin films : contribution of the Dzyaloshinsky-Moriya interaction

Scanning tunnelling spectroscopy (STS) of thin Fe films on W(110) shows that the electronic structures of magnetic domains and domain walls are different. This experimental result is explained on the basis of first-principles calculations. A detailed analysis reveals that the spin–orbit induced mixing between minority dxy+xz and minority dz2 spin states depends on the magnetization direction and changes the local density of states in the vacuum detectable by STS. The effect scales in second or fourth order with the magnetization angle relative to the easy axis. Our finding implies that nanometre-scale magnetic structure information can be obtained even by using non-magnetic probe tips. Magnetization dependent measurements show that the canting of adjacent spins has no major influence on the electronic structure of the sample.