We raise the possibility that the chiral degeneracy of the magnons in ultrathin films can be lifted due to the presence of Dzyaloshinskii-Moriya interactions. By using simple symmetry arguments, we discuss under which conditions such a chiral asymmetry occurs. We then perform relativistic first principles calculations for an Fe monolayer on W(110) and explicitly reveal the asymmetry of the spin-wave spectrum in the case of wave vectors parallel to the (001) direction. Furthermore, we quantitatively interpret our results in terms of a simplified spin model by using calculated Dzyaloshinskii-Moriya vectors. Our theoretical prediction should inspire experiments to explore the asymmetry of spin waves, with a particular emphasis on the possibility to measure the Dzyaloshinskii-Moriya interactions in ultrathin films.

In order to treat the orientation of the magnetic field at surfaces properly, the spin-polarized fully relativistic version of the screened Korringa-Kohn-Rostoker method for semi-infinite systems is presented. Magnetic anisotropy energies up to six iron layers on Au(001) are calculated by using the force theorem, predicting a change from a perpendicular to a parallel magnetization for a layer thickness between three and four layers of Fe, in very good agreement with experimental observations. In particular, the magnetic anisotropy energy is discussed in relation to the orbital magnetic moment and to the orientation of the magnetic field when changed continuously.

In order to explain the anisotropic Rashba-Bychkov effect observed in several metallic-surface-state systems, we use k\ifmmode\cdot\else\textperiodcentered\fi{}p perturbation theory with a simple group-theoretical analysis and construct effective Rashba Hamiltonians for different point groups up to third order in the wave number. We perform relativistic ab initio calculations for the (3\ifmmode\times\else\texttimes\fi{}3)R30$\circ${} Bi/Ag(111) surface alloy, and from the calculated splitting of the band dispersion we find evidence of the predicted third-order terms. Furthermore, we derive expressions for the corresponding third-order Rashba parameters to provide a simple explanation of the qualitative difference concerning the Rashba-Bychkov splitting of the surface states at Au(111) and Bi/Ag(111).

We perform an ab initio study of the ordered phases of IrMn and ${\text{IrMn}}_3$, the most widely used industrial antiferromagnets. Calculation of the form and the strength of the magnetic anisotropy allows the construction of an effective spin model, which is tested against experimental measurements regarding the magnetic ground state and the Néel temperature. Our most challenging result is the extremely strong second-order anisotropy for ${\text{IrMn}}_3$ appearing in its frustrated triangular magnetic ground state, which is surprising since the ordered $L{1}_2$ phase has a cubic symmetry. We explain this large anisotropy by the fact that cubic symmetry is locally broken for each of the three Mn sublattices.

In order to derive tensorial exchange interactions and local magnetic anisotropies in itinerant magnetic systems, an approach combining the spin-cluster expansion with the relativistic disordered local moment scheme is introduced. The theoretical background and computational aspects of the method are described in detail. The exchange interactions and site-resolved anisotropy contributions for the IrMn3/Co(111) interface, a prototype for an exchange bias system, are calculated including a large number of magnetic sites from both the antiferromagnet and ferromagnet. Our calculations reveal that the coupling between the two subsystems is fairly limited to the vicinity of the interface. The magnetic anisotropy of the interface system is discussed, including effects of the Dzyaloshinskii-Moriya interactions that appear due to symmetry breaking at the interface.

An extensive study of the magnetic anisotropy energies (MAE’s) of the high-moment ferromagnetic phase of fcc Fe/Cu(001) overlayers and interlayers is presented in terms of the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker method. Independent of the film thickness for free surfaces the orientation of the magnetization is found to be in-plane, while for capped films a perpendicular magnetization is predicted up to a switching thickness of five Fe monolayers. Based on an analysis of layer-resolved anisotropy energies it is shown that the main contribution to the MAE’s arises from the Fe layer at the Fe/Cu interfaces. Particular features of the MAE’s with respect to the number of cap layers as well as to the film thickness can be viewed in terms of an interfacial hybridization between Fe and Cu. By using the coherent-potential approximation the interdiffusion between the substrate and the magnetic film is shown to reduce the MAE dramatically. © 1996 The American Physical Society.