S. Ohnishi

Local spin density total energy study of surface magnetism: V (100)

Abstract Results of self-consistent all-electron local (spin) density functional studies of the electronic and magnetic properties of vanadium (100) 1-, 3-, 5- and 7-layers films are reported using our full-potential linearized augmented plane wave (FLAPW) method. The calculated work function, 4.2 eV, agrees very well with the experimental value of 4.12 eV. From both Stoner factor analyses and spin-polarized total energy calculations, it is concluded that V(100) undergoes a ferromagnetic phase transition only for the monolayer system. The magnetic moment is found to be 3.09μ B per atom of this monolayer film and to have a total energy 57 mRy below that of the paramagnetic structure. For multilayer V(001) systems, the sharp surface density-of-states peak which is characteristic of the occurrence of surface magnetism in the 3d transition metals is located 0.3 eV above the Fermi level. As a result, the paramagnetic state is stable. In addition, no enhancement of the exchange-correlation integral is found for the surface atoms compared with the bulk value. The lower energy of the paramagnetic structure is further supported by total energy investigations of the multilayer relaxation of V(100) — the calculated interlayer spacings for the paramagnetic surface with a 9% contraction of the topmost interlayer spacing and a 1% expansion of the second interlayer spacing with respect to its bulk value are in good agreement with LEED measurements. It is suggested that the surface magnetism of V(100) may be associated with surface oxygen or caused by impurity induced surface reconstructions.

Magnetism at surfaces and interfaces

Abstract The current state-of-the-art of ab-initio calculations of the magnetic structures of surfaces and interfaces is highlighted by presenting results obtained with the recently developed full-potential linearized augmented plane wave method for thin films. In particular, spin density maps, (induced) magnetic moments and hyperfine-fields are presented for the clean metal surfaces Fe(001), Ni(001) and Pt(001). The magnetic moments on an interface are discussed for the prototypical case Ni/Cu.

Self-consistent FLAPW determination of surface magnetism: Fe(001)☆

Abstract Self-consistent all-electron local density and local spin density (spin-polarized) FLAPW calculations on a 7-layer Fe(001) film are reported. The surface density of states of both cases and the enhancement of the surface magnetic moment to 2.9 μ B , are discussed by comparing with the earlier results of Wang and Freeman and available experiments.

Theoretical determination of surface magnetism (invited)

The theoretical determination of the magnetic structure of surfaces within the (local) spin‐density formalism is briefly described. The feasibility of using such methods for determining delicate magnetic quantities is illustrated by calculation of (1) the Knight shift of the paramagnetic Pt(001) surface, (2) the magnetization of the clean and Ag‐covered Fe(001) surface, and (3) the effect of a p(1×1) H overlayer on the magnetization of a Ni(001) surface. These results demonstrate that it is possible not only to make quantitative predictions for real systems, but more importantly, to gain insight into the underlying physics at surfaces.

Electronic structure and magnetism of surfaces, interfaces and modulated structures (superlattices)

Recent developments in the study of surfaces and interfaces of metals and of artificial materials such as bimetallic sandwiches and modulated structures are described. Key questions include the effects on magnetism of reduced dimensionality and the possibility of magnetically “dead” layers. These developments have stimulated an intensified theoretical effort to investigate and describe the electronic and magnetic structure of surfaces and interfaces. One notable success has been the development of a highly accurate full-potential all-electron method (the FLAPW method) for solving the local spin density equations self-consistently for a single slab geometry. We describe here this advanced state of ab initio calculations in determining the magnetic properties of transition metal surfaces such as those of the ferromagnetic metals Ni(001) and Fe(001) and the Ni/Cu(001) interface. For both clean Fe and Ni(001) we find an enhancement of the magnetic moments in the surface layer. The magnetism of surface and interface Ni layers on Cu(001) (no “dead” layers are found) is described and compared to the clean Ni(001) results. Finally, the role ofμSR experiments in answering some of the questions raised in these studies will be discussed.